Low Temperature Gasification Facility with a Horizontally Oriented Gasifier

ABSTRACT

A low-temperature gasification system comprising a horizontally oriented gasifier is provided that optimizes the extraction of gaseous molecules from carbonaceous feedstock while minimizing waste heat. The system comprises a plurality of integrated subsystems that work together to convert municipal solid waste (MSW) into electricity. The subsystems comprised by the low-temperature gasification system are: a Municipal Solid Waste Handling System; a Plastics Handling System; a Horizontally Oriented Gasifier with Lateral Transfer Units System; a Gas Reformulating System; a Heat Recycling System; a Gas Conditioning System; a Residue Conditioning System; a Gas Homogenization System and a Control System.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35 U.S.C. § 119(e)from U.S. Provisional Application Ser. No. 60/797,973, filed May 5,2006. This application also claims benefit of priority to InternationalPatent Application No. PCT/CA2006/000881, filed Jun. 5, 2006. Thisapplication also claims benefit of priority to International PatentApplication No. PCT/CA2006/000882, filed Jun. 5, 2006. This applicationalso claims benefit of priority under 35 U.S.C. §119(e) from U.S.Provisional Application Ser. No. 60/864,116, filed Nov. 2, 2006. Thisapplication also claims benefit of priority under 35 U.S.C. § 119(e)from U.S. Provisional Application Ser. No. 60/911,179, filed Apr. 11,2007. The contents of all of the aforementioned applications are herebyexpressly incorporated by reference in their entirety and for allpurposes.

FIELD OF THE INVENTION

The present invention pertains to the field of carbonaceous feedstockgasification and to its conversion into syngas and subsequent use togenerate energy.

BACKGROUND OF THE INVENTION

Gasification is a process that enables the conversion of carbonaceousfeedstock, such as municipal solid waste (MSW), biomass, coal, into acombustible gas. The gas can be used to generate electricity, steam oras a basic raw material to produce chemicals and liquid fuels.

Possible uses for the gas include: the combustion in a boiler for theproduction of steam for internal processing and/or other externalpurposes, or for the generation of electricity through a steam turbine;the combustion directly in a gas turbine or a gas engine for theproduction of electricity; fuel cells; the production of methanol andother liquid fuels; as a further feedstock for the production ofchemicals such as plastics and fertilizers; the extraction of bothhydrogen and carbon monoxide as discrete industrial fuel gases; andother industrial applications.

Generally, the gasification process consists of feeding carbonaceousfeedstock into a heated chamber (the gasifier) along with a controlledand/or limited amount of oxygen and optionally steam. In contrast toincineration or combustion, which operate with excess oxygen to produceCO₂, H₂O, SO_(x), and NO_(x), gasification processes produce a raw gascomposition comprising CO, H₂, H₂S, and NH₃. After clean-up, the primarygasification products of interest are H₂ and CO.

Useful feedstock can include any municipal waste, waste produced byindustrial activity and biomedical waste, sewage, sludge, coal, heavyoils, petroleum coke, heavy refinery residuals, refinery wastes,hydrocarbon contaminated soils, biomass, and agricultural wastes, tires,and other hazardous waste. Depending on the origin of the feedstock, thevolatiles may include H₂O, H₂, N₂, O₂, CO₂, CO, CH₄, H₂S, NH₃, C₂H₆,unsaturated hydrocarbons such as acetylenes, olefins, aromatics, tars,hydrocarbon liquids (oils) and char (carbon black and ash).

As the feedstock is heated, water is the first constituent to evolve. Asthe temperature of the dry feedstock increases, pyrolysis takes place.During pyrolysis the feedstock is thermally decomposed to release tars,phenols, and light volatile hydrocarbon gases while the feedstock isconverted to char.

Char comprises the residual solids consisting of organic and inorganicmaterials. After pyrolysis, the char has a higher concentration ofcarbon than the dry feedstock and may serve as a source of activatedcarbon. In gasifiers operating at a high temperature (>1,200° C.) or insystems with a high temperature zone, inorganic mineral matter is fusedor vitrified to form a molten glass-like substance called slag.

Since the slag is in a fused, vitrified state, it is usually found to benon-hazardous and may be disposed of in a landfill as a non-hazardousmaterial, or sold as an ore, road-bed, or other construction material.It is becoming less desirable to dispose of waste material byincineration because of the extreme waste of fuel in the heating processand the further waste of disposing ash as a residual waste, materialthat can be converted into a useful syngas and solid material.

The means of accomplishing a gasification process vary in many ways, butrely on four key engineering factors: the atmosphere (level of oxygen orair or steam content) in the gasifier; the design of the gasifier; theinternal and external heating means; and the operating temperature forthe process. Factors that affect the quality of the product gas include:feedstock composition, preparation and particle size; gasifier heatingrate; residence time; the plant configuration including whether itemploys a dry or slurry feed system, the feedstock-reactant flowgeometry, the design of the dry ash or slag mineral removal system;whether it uses a direct or indirect heat generation and transfermethod; and the syngas cleanup system. Gasification is usually carriedout at a temperature in the range of about 650° C. to 1200° C., eitherunder vacuum, at atmospheric pressure or at pressures up to about 100atmospheres.

There are a number of systems that have been proposed for capturing heatproduced by the gasification process and utilizing such heat to generateelectricity, generally known as combined cycle systems.

The energy in the product gas coupled with substantial amounts ofrecoverable sensible heat produced by the process and throughout thegasification system can generally produce sufficient electricity todrive the process, thereby alleviating the expense of local electricityconsumption. The amount of electrical power that is required to gasify aton of a carbonaceous feedstock depends directly upon the chemicalcomposition of the feedstock.

If the gas generated in the gasification process comprises a widevariety of volatiles, such as the kind of gas that tends to be generatedin a low temperature gasifier with a “low quality” carbonaceousfeedstock, it is generally referred to as off-gas. If thecharacteristics of the feedstock and the conditions in the gasifiergenerate a gas in which CO and H₂ are the predominant chemical species,the gas is referred to as syngas. Some gasification facilities employtechnologies to convert the raw off-gas or the raw syngas to a morerefined gas composition prior to cooling and cleaning through a gasquality conditioning system.

Utilizing plasma heating technology to gasify a material is a technologythat has been used commercially for many years. Plasma is a hightemperature luminous gas that is at least partially ionized, and is madeup of gas atoms, gas ions, and electrons. Plasma can be produced withany gas in this manner. This gives excellent control over chemicalreactions in the plasma as the gas might be neutral (for example, argon,helium, neon), reductive (for example, hydrogen, methane, ammonia,carbon monoxide), or oxidative (for example, air, oxygen, carbondioxide). In the bulk phase, a plasma is electrically neutral.

Some gasification systems employ plasma heat to drive the gasificationprocess at a high temperature and/or to refine the offgas/syngas byconverting, reconstituting, or reforming longer chain volatiles and tarsinto smaller molecules with or without the addition of other inputs orreactants when gaseous molecules come into contact with the plasma heat,they will disassociate into their constituent atoms. Many of these atomswill react with other input molecules to form new molecules, whileothers may recombine with themselves. As the temperature of themolecules in contact with the plasma heat decreases all atoms fullyrecombine. As input gases can be controlled stoichiometrically, outputgases can be controlled to, for example, produce substantial levels ofcarbon monoxide and insubstantial levels of carbon dioxide.

The very high temperatures (3000 to 7000° C.) achievable with plasmaheating enable a high temperature gasification process where virtuallyany input feedstock including waste in as-received condition, includingliquids, gases, and solids in any form or combination can beaccommodated. The plasma technology can be positioned within a primarygasification chamber to make all the reactions happen simultaneously(high temperature gasification), can be positioned within the system tomake them happen sequentially (low temperature gasification with hightemperature refinement), or some combination thereof.

The gas produced during the gasification of carbonaceous feedstock isusually very hot but may contain small amounts of unwanted compounds andrequires further treatment to convert it into a useable product. Once acarbonaceous material is converted to a gaseous state, undesirablesubstances such as metals, sulfur compounds and ash may be removed fromthe gas. For example, dry filtration systems and wet scrubbers are oftenused to remove particulate matter and acid gases from the gas producedduring gasification. A number of gasification systems have beendeveloped which include systems to treat the gas produced during thegasification process.

These factors have been taken into account in the design of variousdifferent systems which are described, for example, in U.S. Pat. Nos.6,686,556, 6,630,113, 6,380,507; 6,215,678, 5,666,891, 5,798,497,5,756,957, and U.S. Patent Application Nos. 2004/0251241, 2002/0144981.There are also a number of patents relating to different technologiesfor the gasification of coal for the production of synthesis gases foruse in various applications, including U.S. Pat. Nos. 4,141,694;4,181,504; 4,208,191; 4,410,336; 4,472,172; 4,606,799; 5,331,906;5,486,269, and 6,200,430.

Prior systems and processes have not adequately addressed the problemsthat must be dealt with on a continuously changing basis. Some of thesetypes of gasification systems describe means for adjusting the processof generating a useful gas from the gasification reaction. Accordingly,it would be a significant advancement in the art to provide a systemthat can efficiently gasify carbonaceous feedstock in a manner thatmaximizes the overall efficiency of the process, and/or the stepscomprising the overall process.

This background information is provided for the purpose of making knowninformation believed by the applicant to be of possible relevance to thepresent invention. No admission is necessarily intended, nor should beconstrued, that any of the preceding information constitutes prior artagainst the present invention.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a low temperaturegasification facility with a horizontally oriented gasifier.

In accordance with an aspect of the present invention, there is provideda low-temperature system for the conversion of carbonaceous feedstockinto syngas of a defined composition, said system comprising ahorizontally oriented gasifier for conversion of carbonaceous feedstockinto off-gas and solid residue, said gasifier having a feedstock inputmeans, gas outlet means and a solid residue outlet means and comprisinga stepped floor, wherein each step is provided with a moving shelflateral transfer means for moving material through said gasifier duringprocessing; a gas reformulating subsystem for the conversion of off-gasproduced in said gasifier into syngas containing CO and H₂; a residueconditioning subsystem for melting and homogenizing said solid residue,and a control system to regulate the operation of the system.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures.

FIG. 1 is a flow diagram showing the different regions of the gasifierin general terms.

FIG. 2 is a representation of the gasification processes occurring inRegions 1, 2 and 3 of one embodiment of the gasifier.

FIG. 3 depicts an overview process flow diagram of a low-temperaturegasification facility incorporating an exemplary gas conditioning systemaccording to one embodiment of the invention, integrated with downstreamgas engines.

FIG. 4 is a site layout for the entire gasification system.

FIG. 5 shows the layout of the storage building for the municipal solidwaste.

FIG. 5A shows the view of the waste handling system.

FIG. 5B shows a schematic of the plastics handling system.

FIG. 6 is a perspective view of one embodiment of the gasifier,detailing the feedstock input, gas outlet, residue outlet, carrier-ramenclosure and access ports.

FIG. 7 is a side view of the gasifier illustrated in FIG. 6 detailingthe air boxes, residue can and dust collector.

FIG. 8 is a central longitudinal cross-sectional view through thegasifier illustrated in FIGS. 6 and 7, detailing the feedstock input,gas outlet, residue outlet, lateral transfer means, thermocouples andaccess ports.

FIG. 9 illustrates a blown up cross sectional view detailing the airboxes, carrier-ram fingers, residue extractor screw and serrated edge ofstep C.

FIG. 10 is a sectional view of the gasifier of FIGS. 6 and 7 detailingthe refractory.

FIG. 11 details the air box assembly of Step A and B of the gasifierillustrated in FIGS. 6 to 10.

FIG. 12 illustrates a cross sectional view of the Step C air box of thegasifier illustrated in FIGS. 6 to 10.

FIG. 13 illustrates a cross sectional view of the gasifier of FIGS. 6 to10 detailing an air box.

FIG. 14 details the dust seal of the multi-finger carrier-ram of thegasifier illustrated in FIGS. 6 to 10.

FIG. 15 showing the dust removal system of one embodiment of thegasifier illustrated in FIGS. 6 to 10 detailing the dust pusher, dustcan attachment, shutter, operator handle and chain mechanism.

FIG. 16 details the carrier-ram enclosure of the gasifier illustrated inFIGS. 6, 7, 8, 9 & 10 detailing the carrier-ram structure.

FIG. 17 is an illustration detailing the level switch locations in oneembodiment of the invention.

FIG. 18 shows the setup of the gasifier, gas reformulating chamber andthe residue conditioning chamber.

FIG. 19 is a cross-sectional view of the setup of the gasifier, gasreformulating chamber and the residue conditioning chamber.

FIG. 20 is a schematic of the gas reformulating chamber.

FIG. 21 is a view of the inner wall of the reformulating chamber.

FIG. 22 is a top-down view of the reformulating chamber showing theposition of the torches, and the air and steam nozzles.

FIG. 23 shows the arrangement of the swirl inlets around thereformulating chamber.

FIG. 24 shows the attachment of a plasma torch on the reformulatingchamber.

FIG. 25A is a cross-sectional view of the reformulating chamber of FIG.20.

FIG. 25B is a diagram illustrating the air-flow within a gasifiercomprising the gas reformulating system of the invention including thereformulating chamber of FIG. 20.

FIG. 25C illustrates the injection of air from the air inputs into thereformulating chamber of FIG. 20 and its effect on air-flow within;

FIG. 26 is a functional block diagram of the residue conditioningsystem.

FIG. 27 shows a view of the actual implementation of the residueconditioning system and its connections to the gasifier and the baghousefilter.

FIG. 28 shows a cross-sectional view of the residue conditioningchamber.

FIG. 29 shows another view of the residue conditioning chamber.

FIG. 30 shows a view of the residue conditioning chamber and the quenchtank with the conveyor used for the transfer of vitrified slag to theslag stockpile.

FIG. 31 shows the entire residue conditioning system from another angleand also shows the support structure used for the residue conditioningchamber.

FIG. 32 shows the arrangement of the residue gas conditioning systemwith the residue conditioning chamber.

FIG. 32B shows another view of the residue gas conditioning system withthe residue conditioning chamber.

FIG. 33 depicts a process flow diagram of the entire system, and inparticular the gas conditioning system (GCS).

FIG. 34 depicts the setup of the gas conditioning system integrated witha syngas regulation system according to one embodiment of the presentinvention.

FIG. 35 is a more detailed drawing of the heat exchanger and shows theprocess air blower used for the control of the air input to the heatexchanger.

FIG. 36 depicts a dry injection system whereby activated carbon or otheradsorbents is held in a storage hopper and is fed into the syngas streamby rotating screw. The syngas stream pipe is angled so that carbon notentrained in the gas stream rolls into the baghouse.

FIG. 37 presents an exemplary schematic diagram of the dry injectionsystem in combination with the baghouse.

FIG. 38 presents an exemplary schematic diagram of the HCl scrubber andassociated components.

FIG. 39 shows a system for collecting and storing waste water from thegas conditioning system.

FIG. 40 depicts a process flow diagram of an H₂S removal process using aThiopaq-based bioreactor, in accordance with one embodiment of theinvention.

FIG. 41 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered from asingle source to a single homogenization chamber and then delivered tomultiple engines, each engine having its own gas/liquid separator andheater.

FIG. 42 is an illustration of a fixed-volume homogenization chamber, inaccordance with an embodiment of the invention.

FIG. 43 is a high-level schematic diagram of a gasification system andcontrol system therefore;

FIG. 44 is an alternative diagrammatic representation of thegasification and control systems of FIG. 43;

FIG. 45 is a flow diagram of a control scheme for controlling thegasification system of FIGS. 43 and 44;

FIG. 46 is a flow diagram of an alternative control scheme forcontrolling the gasification system of FIGS. 43 and 44, wherein thissystem is further adapted for using process additive steam in agasification process thereof.

FIG. 47 is a cross-sectional view through one embodiment of thegasifier, detailing the feedstock input, gas outlet, ash outlet, lateraltransfer system, additive ports and access ports.

FIG. 48 is a central longitudinal cross-sectional view through theembodiment of the gasifier illustrated in FIG. 47, detailing thethermocouples and process additive ports.

FIG. 49 is a perspective view of the embodiment of the gasifierillustrated in FIGS. 47 and 48.

FIG. 50 illustrates a view of the outside of the embodiment of thegasifier illustrated in FIGS. 47 to 49 detailing the external elementsof the lateral transfer system.

FIG. 51 illustrates a portion of a lateral transfer unit of the gasifierillustrated in FIGS. 47 to 49.

FIG. 52 illustrates a bottom view of the lateral transfer unitillustrated in FIG. 51.

FIG. 53 illustrates an alternative embodiment of the lateral transferunit illustrated in FIG. 51.

FIG. 54 is a schematic of one embodiment gas reformulating system of theinvention coupled to two gasifiers.

FIGS. 55 A and B illustrates an arrangement of baffles in one embodimentof the gas reformulating chamber of the invention. FIG. 6A is a diagramillustrating air-flow within the gas reformulating chamber comprisingbridge wall baffles. FIG. 6B is a diagram illustrating air-flow withinthe gas reformulating chamber comprising turbulator or choke ringbaffles.

FIG. 56 is a schematic of a transport reactor comprising one embodimentof the gas reformulating system.

FIG. 57 is a schematic of two entrained flow gasifiers comprising oneembodiment of the gas reformulating system.

FIG. 58 is a schematic of two fixed bed gasifier comprising oneembodiment of the gas reformulating system.

FIG. 59 is a schematic of a cyclonic gasifier comprising one embodimentof the gas reformulating system.

FIG. 60 is a block flow diagram of the recovery of heat from the syngasproduct of the gasification process using a heat exchanger and a heatrecovery steam generator, according to one embodiment of the presentinvention.

FIG. 61 is a block flow diagram of a system for cooling hot raw syngasproducts, including a heat exchanger for recovery of heat from the rawsyngas product of the gasification process, and a quench step forfurther syngas cooling, according to one embodiment of the presentinvention.

FIG. 62A is a schematic diagram showing the functional requirements fora converter gas-to-air heat exchanger, according to one embodiment ofthe present invention.

FIG. 62B is a schematic diagram depicting a gas-to-air heat exchanger,according to one embodiment of the present invention.

FIG. 63 is a schematic diagram showing a piping system to transfer theexchange-air to the converter, according to one embodiment of thepresent invention.

FIG. 64 is a schematic diagram depicting the relationship between agas-to-air heat exchanger and a heat recovery steam generator, accordingto one embodiment of the present invention.

FIG. 65 is a schematic diagram showing a high level view of a syngasflow/pressure is control subsystem, according to one embodiment of thepresent invention.

FIG. 66 is a schematic diagram depicting a high level concept of varioustemperature controls within the system, according to one embodiment ofthe present invention.

FIG. 67A to 67 K are block flow diagrams depicting overviews of variousembodiments of the present invention.

FIGS. 68 to 75 depict various combinations of processes comprisingdifferent embodiments of the GCS.

FIG. 76 is a block flow diagram showing the inputs, optional inputs andoutputs of a residue conditioning system of the present invention;

FIG. 77 is a schematic representation of a typical residue conditioningchamber in accordance with the present invention;

FIG. 78A is a schematic depiction of a residue conditioning chamber inindirect communication with two residue sources, in accordance with oneembodiment of the present invention;

FIG. 78B is a schematic depiction of a residue conditioning chamber inindirect communication with one residue source, in accordance with oneembodiment of the present invention;

FIG. 79 illustrates a cross-sectional view of one embodiment of aresidue conditioning chamber integrated with a residue conditioningchamber;

FIG. 80 is a partial cross-sectional view of an S-spout type slagoutlet, in accordance with one embodiment of the present invention;

FIG. 81 is a partial cross-sectional view of a tiltable slag crucible ina residue conditioning chamber in accordance with one embodiment of thepresent invention;

FIG. 82 is a partial cross-sectional view of one embodiment of a slagoutlet, in accordance with the present invention;

FIG. 83 is a partial cross-sectional view of one embodiment of a slagoutlet, in accordance with the present invention;

FIG. 84 is a partial cross-sectional view of one embodiment of a slagoutlet, in accordance with the present invention;

FIG. 85 is a partial cross-sectional view of one embodiment of a slagoutlet, in accordance with the present invention;

FIG. 86 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered from asingle source to a single homogenization chamber and then delivered to asingle engine by way of a gas conditioning skid.

FIG. 87 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered from asingle source to a single homogenization chamber and then delivered to asingle engine by way of a heater, filter and a pressure regulator valve.

FIG. 88 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered from asingle source to a single homogenization chamber and then delivered tomultiple engines by way of a heater and a plurality of filters andpressure regulator valves.

FIG. 89 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered frommultiple sources to a single homogenization chamber and then deliveredto multiple engines, each engine having its own gas conditioning skid.

FIG. 90 is an illustration of a gas homogenization system, in accordancewith one embodiment of the invention, where gas is delivered to multipleengines from two parallel streams, each stream comprising a singlesource of gas delivered to a single homogenization chamber.

FIG. 91 is an illustration of a constant-volume homogenization chamber,in accordance with one embodiment of the invention.

FIG. 92 is an illustration of a homogenization chamber configured aspressure vessel and compressor combination, in accordance with oneembodiment of the invention.

FIG. 93 is an illustration of a homogenization chamber configured as adouble membrane gas holder, in accordance with one embodiment of theinvention.

FIG. 94 is an illustration of a homogenization chamber configured as anabsorption-type gas holder, in accordance with one embodiment of theinvention.

FIG. 95 is an illustration of a plurality of constant-volumehomogenization chambers arranged in parallel, in accordance with oneembodiment of the invention.

FIG. 96 is a flow diagram depicting the use of a control system tocontrol a gasification process for converting a carbonaceous feedstockinto gas, in accordance with one embodiment of the present invention.

FIG. 97 is a schematic diagram of a computing platform, and exemplarycomponents thereof, of a control system to control a gasificationprocess for converting a carbonaceous feedstock into a gas, inaccordance with one embodiment of the present invention.

FIG. 98 is a schematic diagram of a centralized control system, inaccordance with one embodiment of the present invention.

FIG. 99 is a schematic diagram of an at least partially distributedcontrol system, in accordance with one embodiment of the presentinvention.

FIG. 100 is a schematic diagram depicting exemplary sensing and responsesignals respectively received from and transmitted to a gasificationsystem by a control system to control one or more processes implementedtherein, in accordance with one embodiment of the present invention.

FIG. 101 is a schematic diagram depicting exemplary sensing and responseaccess points of the integrated system control system to variousdevices, modules and subsystems of a system for the conversion ofcarbonaceous feedstocks to a gas of a specified composition, along withvarious possible downstream applications, in accordance with variousexemplary embodiments of the present invention.

FIG. 102 is a schematic diagram depicting a control system forcontrolling inputs to a converter of a system for the conversion ofcarbonaceous feedstock into a gas, in accordance with one embodiment ofthe present invention.

FIG. 103 is a flow diagram of a control scheme for controlling thegasification system.

FIG. 104 is a flow diagram of an alternative control scheme forcontrolling the gasification system, wherein this system is furtheradapted for using process additive steam in a gasification processthereof.

FIG. 105 is a flow diagram of an alternative control scheme forcontrolling a gasification process, in accordance with a furtherexemplary embodiment of the present invention.

FIG. 106 is a flow diagram of an alternative control scheme forcontrolling a gasification process, in accordance with a furtherexemplary embodiment of the present invention.

FIGS. 107 to 110 depict various combinations of how the processes of thefacility can be constructed, wherein “1” depicts zone 1 (a gasifier),“2” depicts zone 2 (a residue conditioner) and “3” depicts zone 3 (a gasreformulating system).

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the term “about” refers to a +/−10% variation from thenominal value. It is to be understood that such a variation is alwaysincluded in any given value provided herein, whether or not it isspecifically referred to.

The terms “carbonaceous feedstock” and “feedstock,” as usedinterchangeably herein, are defined to refer to carbonaceous materialthat can be used in the gasification process. Examples of suitablefeedstock include, but are not limited to, waste materials, includingmunicipal wastes; wastes produced by industrial activity; biomedicalwastes; carbonaceous material inappropriate for recycling, includingnon-recyclable plastics; sewage sludge; coal; heavy oils; petroleumcoke; heavy refinery residuals; refinery wastes; hydrocarboncontaminated solids; biomass; agricultural wastes; municipal solidwaste; hazardous waste and industrial waste. Examples of biomass usefulfor gasification include, but are not limited to, waste wood; freshwood; remains from fruit, vegetable and grain processing; paper millresidues; straw; grass, and manure.

The term “waste materials” is defined to refer to carbonaceous hazardousand non-hazardous wastes. These can include municipal wastes, wastesproduced by industrial activity and biomedical wastes. Waste materialsalso include carbonaceous material inappropriate for recycling,including non-recyclable plastics, and sewage sludge.

The term “controllable solids movement means” is defined to refer to oneor more devices for removing solids from the gasifier in a controllablemanner. Examples of such devices include, but are not limited to,rotating arms, rotating wheels, rotating paddles, moving shelves, pusherrams, screws, conveyors, and combinations thereof.

The term “sensing element” is defined to describe any element of thesystem configured to sense a characteristic of a process, a processdevice, a process input or process output, wherein such characteristicmay be represented by a characteristic value useable in monitoring,regulating and/or controlling one or more local, regional and/or globalprocesses of the system. Sensing elements considered within the contextof a gasification system may include, but are not limited to, sensors,detectors, monitors, analyzers or any combination thereof for thesensing of process, fluid and/or material temperature, pressure, flow,composition and/or other such characteristics, as well as materialposition and/or disposition at any given point within the system and anyoperating characteristic of any process device used within the system.It will be appreciated by the person of ordinary skill in the art thatthe above examples of sensing elements, though each relevant within thecontext of a gasification system, may not be specifically relevantwithin the context of the present disclosure, and as such, elementsidentified herein as sensing elements should not be limited and/orinappropriately construed in light of these examples.

The term “response element” is defined to describe any element of thesystem configured to respond to a sensed characteristic in order tooperate a process device operatively associated therewith in accordancewith one or more pre-determined, computed, fixed and/or adjustablecontrol parameters, wherein the one or more control parameters aredefined to provide a desired process result. Response elementsconsidered within the context of a gasification system may include, butare not limited to static, pre-set and/or dynamically variable drivers,power sources, and any other element configurable to impart an action,which may be mechanical, electrical, magnetic, pneumatic, hydraulic or acombination thereof, to a device based on one or more controlparameters. Process devices considered within the context of agasification system, and to which one or more response elements may beoperatively coupled, may include, but are not limited to, materialand/or feedstock input means, heat sources such as plasma heat sources,additive input means, various gas blowers and/or other such gascirculation devices, various gas flow and/or pressure regulators, andother process devices operable to affect any local, regional and/orglobal process within a gasification system. It will be appreciated bythe person of ordinary skill in the art that the above examples ofresponse elements, though each relevant within the context of agasification system, may not be specifically relevant within the contextof the present disclosure, and as such, elements identified herein asresponse elements should not be limited and/or inappropriately construedin light of these examples.

The term “real-time” is defined to define any action that issubstantially reflective of the present or current status of the systemor process, or a characteristic thereof, to which the action relates. Areal-time action may include, but is not limited to, a process, aniteration, a measurement, a computation, a response, a reaction, anacquisition of data, an operation of a device in response to acquireddata, and other such actions implemented within the system or a givenprocess implemented therein. It will be appreciated that a real-timeaction related to a relatively slow varying process or characteristicmay be implemented within a time frame or period (e.g. second, minute,hour, etc.) that is much longer than another equally real-time actionrelated to a relatively fast varying process or characteristic (e.g. 1ms, 10 ms, 100 ms, 1 s).

The term “continuous” is defined to define any action implemented on aregular basis or at a given rate or frequency. A continuous action mayinclude, but is not limited to, a process, an iteration, a measurement,a computation, a response, a reaction, an acquisition of data via asensing element, an operation of a device in response to acquired data,and other such actions implemented within the system or in conjunctionwith a given process implemented therein. It will be appreciated that acontinuous action related to a relatively slow varying process orcharacteristic may be implemented at a rate or frequency (e.g.once/second, once/minute, once/hour, etc.) that is much slower thananother equally continuous action related to a relatively fast varyingprocess or characteristic (e.g. 1 KHz, 100 Hz, 10 Hz, 1 Hz).

As used herein, the term “converter” refers to the system used toconvert carbonaceous feedstock into a gas product prior to cooling andconditioning. The conversion process can occur in one chamber, onechamber with multiple zones, or multiple chambers. In one embodiment,the converter comprises a gasifier and a gas reformulation system.

As used herein, the term “product gas” means generally, the gasgenerated by the gasification facility, prior to cooling and cleaning byprocesses designated to remove contaminants. Depending on the design ofthe gasification facility it can be used to refer to, for example, rawoffgas, raw syngas, reformulated offgas or reformulated syngas.

As used herein, the term “gas reformulating” means further processingraw syngas or raw off-gas to generate gas of a different chemicalcomposition. Air, enriched air, steam, etc, can be used in combinationwith plasma heat to change the levels of CO/CO₂ and H₂/H₂O (desiredheating value).

As used herein, the term “reformulated syngas” means off-gas that hasbeen passed through a reformulating step whereby additives such as heat,air and/or steam have been used to transform the gas from one chemicalcomposition to gas of another chemical composition (optimized heatingvalue). For example, this gas has passed through a Gas ReformulatingSystem (GRS).

As used herein, the term “reformulated off-gas” means off-gas that hasbeen passed through a reformulating step whereby additives such as heat,air and/or steam have been used to transform the gas from one chemicalcomposition to gas of another chemical composition (desired heatingvalue). For example, this gas has passed through a Gas ReformulatingSystem (GRS).

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

This invention provides a gasification facility for the conversion ofcarbonaceous feedstock into gas with further optional downstreamapplications such as the generation of energy. The facility comprises anumber of systems that work together to function as an integrated systemfor the conversion feedstock into electricity. One skilled in the artcan appreciate, however, that each subsystem on its own can beconsidered as a system that could function with other systems and/or beincorporated into other facilities. The subsystems comprising thefacility of this invention are: a Municipal Solid Waste Handling System;a Plastics Handling System; a Horizontally Oriented Gasifier withLateral Transfer Units System; a Gas Reformulating System; a HeatRecycling System; a Gas Conditioning System; a Residue ConditioningSystem; a Gas Homogenization System and a Control System.

The configuration of the various components that are comprised by thegasification facility in one embodiment of the present invention isdepicted schematically in FIG. 3.

In accordance with one embodiment of the present invention, thegasification system comprises an integrated control system forcontrolling the gasification process implemented therein, which mayinclude various independent and interactive local, regional and globalprocesses.

A high-level process control schematic that depicts various sensing andresponse elements comprised by or associated with the components of thegasification facility in one embodiment of the invention is depicted inFIG. 43.

The control system may be configured to enhance, and possibly optimisethe various processes for a desired front end and/or back end result.

For instance, a front-to-back control scheme could include facilitatingthe constant throughput of feedstock, for example in a system configuredfor the gasification of MSW, while meeting regulatory standards for thistype of system. Such front-to-back control scheme could be optimised toachieve a given result for which the system is specifically designedand/or implemented, or designed as part of a subset or simplifiedversion of a greater control system, for instance upon start-up orshut-down of the process or to mitigate various unusual or emergencysituations.

A back-to-front control scheme could include the optimisation of aproduct gas quality or characteristic for a selected downstreamapplication, namely the generation of electricity via downstream gasengine(s) in this example. While the control system could be configuredto optimise such back-end result, monitoring and regulation of front-endcharacteristics could be provided in order to ensure proper andcontinuous function of the system in accordance with regulatorystandards, when such standards apply.

It will be apparent to the person of skill in the art that the aboveexamples are not meant to be limiting and that other examples offront-end and back-end results may be considered herein withoutdeparting from the general scope and nature of the present disclosure.Furthermore, the person of skill in the art will appreciate that thecontrol system may be configured to provide complimentary results whichmay be best defined as a combination of front-end and back-end results,or again as a result flowing from any point within the system.

Municipal Solid Waste (MSW) Handling System

The initial MSW handling system is designed to take into account: (a)storage capability for supply of four days; (b) avoidance of longholding periods and excess decomposition of MSW; (c) prevention ofdebris being blown around; (d) control of odour; (e) access and turningspace for garbage trucks to unload; (f) minimization of driving distanceand amount of turning required by the loader transporting MSW from theMSW stockpile to the MSW shredding system (g) avoidance of operationalinterference between loader and garbage trucks; (h) possibility ofadditional gasification streams to allow for plant expansion; (i)minimum intrusion by trucks into the facility, especially into hazardousareas; (j) safe operation with minimum personnel; (k) indication for theloader operator of the fill levels in the conveyor input hoppers; (l)shredding the as-received waste to a particle size suitable forprocessing; and (m) remote controllability of MSW flow rate into theprocessor and independent control of the plastics feed rate.

The MSW handling system comprises a MSW storage building, a loader, aMSW shredding system, a magnetic separator and a feed conveyor. Aseparate system is also designed for storing, shredding, stockpiling andfeeding plastics, the feed-rate of which is used as an additive in thegasification process. All processing of both MSW and the plastics aredone inside buildings to contain debris and odor. A first-in-first-out(FIFO) scheduling approach is used to minimize excessive decompositionof the MSW. A mechanized, bucket-based loader is used to transfermaterial from the stockpile to the shredding system.

The MSW shredding system consists of an input conveyor, a shredder and apick conveyor. The input conveyor transports the MSW from inside thebuilding into a shredder. The conveyor is controlled remotely by theprocess controller to match process demands. The shredder ensures thatthe as-received MSW is suitable for processing. The shredder is equippedto detect any possible jams and take appropriate action. The shreddedwaste is dropped onto a belt conveyor, transported under a magneticpick-up system that avoids inadvertent feeding of excessive amounts offerrous metals through the gasifier. After this step, the MSW is droppedonto a screw conveyor which feeds the MSW into the gasifier. The feedrate of the screw conveyor is controlled by the process controller tomeet process demands. The MSW feed conveyor has an additional entry toaccept shredded plastic.

Plastics Handling System

The system for handling plastics provides storage for the plastic, shredit, place it into a stockpile and feed it under independent control intothe processor. The system comprises a storage facility, a shredder withinput hopper, a take-away conveyor and a stockpile, all located in acommon building to control debris. A feed conveyor moves the shreddedplastic into the gasifier. The conveyor trough is sealed to the troughof the MSW conveyor such that the plastic is introduced into thegasifier via the MSW conveyor to reduce openings into the gasifier. Theconveyor is a screw conveyor with the hopper sealed to it to provide gassealing when it contains material.

A Horizontally Oriented Gasifier with Lateral Transfer Units System

This system comprises a horizontally-oriented gasification chamberhaving one or more feedstock inputs, one or more gas outputs and a solidresidue output; a chamber heating system; one or more lateral transferunits for moving material through said gasifier during processing; and acontrol system for controlling movement of said one or more lateraltransfer units.

This system enables extraction of volatiles throughout the variousstages of gasification of carbonaceous feedstock to be optimized.Feedstock is introduced at one end of the gasifier and is moved throughthe gasifier during processing by one or more lateral transfer units.The temperature at the top of the material pile generally increases asgasification proceeds through drying, volatilization, char-to-ashconversion with the simultaneous production of CO and CO₂. A controlsystem obtains information from measurable parameters such astemperature and pile height or profile and manages the movement of eachlateral transfer unit independently.

To facilitate movement of reactant material, the individual lateraltransfer units can be controlled independently or a group of two or morelateral transfer units can be controlled in a coordinated manner. Thepreferred number of lateral transfer units in a particular gasifier isdependent on the path length reactant material must travel and thedistance reactant material can be moved by each lateral transfer unitand is a compromise between minimizing the magnitude of processdisturbances caused by each discrete transfer and mechanical complexity,cost, and reliability.

Thus, each area in the horizontally-oriented gasifier can experiencetemperature ranges and optional process additives (such as air, oxygenand/or steam) that promote a certain stage of the gasification process.In a pile of reactant material, all stages of gasification are occurringconcurrently, however individual stages are favored at a certaintemperature range.

By physically moving the material through the gasifier, the gasificationprocess can be facilitated by allowing as much drying as energeticallyefficient to occur prior to raising the temperature of the material topromote volatilization. The process then seeks to allow as muchvolatilization as energetically efficient to occur prior to raising thetemperature of the material to promote char-to-ash conversion.

In one embodiment, the ash is translocated into an ash collectionchamber. Appropriate ash collection chambers are known in the art andaccordingly, a worker skilled in the art having regard to therequirements of the system would readily know the size, shape andmanufacture of an appropriate ash collection chamber. In one embodiment,the ash will be translocated into a water tank for cooling, from whichthe gasifier residue is transmitted through a conduit, optionally, undercontrol of a valve, to a point of discharge. In one embodiment, the ashis translocated into a separate slag conversion chamber for theconversion of ash-to-slag.

During processing, feedstock is introduced into the chamber at one end;hereafter referred to as the feed end, through the feedstock input andis transported from the feed end through the various regions in thegasification chamber towards the ash (solid residue) output or ash end.As the feed material progresses through the chamber, it loses its massand volume as its volatile fraction is volatilized to form off-gas andthe resulting char is reacted to form additional off-gas and ash.

Due to this progressive conversion, the height of the material (pileheight) decreases from the feed end to the ash end of the chamber andlevels off when only solid residue (ash) remains.

In one embodiment, the off-gas escapes through the gas output into, forexample, a gas refinement chamber where it can undergo furtherprocessing or into a storage chamber or tank. The solid residue (ash) istransported through the ash output to, for example, an ash collectionchamber or a solid residue conditioning chamber for further processing.

In one embodiment, as shown in FIG. 47, the gasifier has a stepped floorhaving a plurality of floor levels or steps. Optionally, each floorlevel is sloped between about 5 and about 10 degrees.

In one embodiment of the step-floor gasifier, the individual steps(floor levels) correlate, at least in part, with the individual regionsdiscussed above, with each region or step having conditions optimizedfor different degrees of drying, volatilization and carbon conversion.For convenience, the uppermost step will be referred to as step A; thenext step will be referred to as step B, etc. Corresponding lateraltransfer units will be identified with the same letter, i.e. lateraltransfer unit A or ram A services step A, lateral transfer unit B or ramB services step B.

In the three step embodiment, there is an upper step or step A, middlestep or step B and a lower step or step C. The feed material is fed ontothe first step (step A). The normal temperature range for this step (asmeasured at the bottom of the material pile) lies between 300 and 900°C. Step B is designed to have a bottom temperature range between 400 and950° C. to promote volatilization with the remainder of the dryingoperation as well as a substantial amount of carbon conversion. Step Ctemperature range lies between 500 and 1000° C. The major process inStep C is that of carbon conversion with a lesser amount (the remainder)of volatilization. In one embodiment, movement over the steps isfacilitated by the lateral transfer system with each step optionallybeing serviced by an independently controlled lateral transfer unit.

During processing, air as a source of oxygen is introduced into thechamber. Optionally, the method of injecting process air can be selectedto facilitate an even flow of air into the gasification chamber, preventhot spot formation and/or improve temperature control. The air can beintroduced through the sides of the chamber, for example as shown inFIGS. 47 and 48, optionally from near the bottom of the chamber, or canbe introduced through the floor of the chamber, or through both.

Also to be considered in the design of the gasifier is the position,orientation and number of the process additive inputs. The processadditives can optionally be injected into the gasifier at locationswhere they will ensure most efficient reaction to achieve the desiredconversion result. In one embodiment, the floor of the gasificationchamber is perforated to varying degrees to allow for introduction ofprocess additives, such as air at the base of the material pile.

In one embodiment, the side-walls of the chamber slope inwards towardsthe bottom to achieve a small enough width for good air penetration fromthe sides while still having the required volume of material. The slopeangle can optionally be made steep enough to assure that the materialwill drop towards the bottom of the chamber during processing.

The gasification chamber is a partially or fully refractory-linedchamber with an internal volume sized to accommodate the appropriateamount of material for the required solids residence time. Therefractory protects the gasification chamber from the high temperatureand corrosive gases and minimizes unnecessary loss of heat from theprocess. The refractory material can be a conventional refractorymaterial well-known to those skilled in the art and which is suitablefor use for a high temperature e.g. up to about 1100° C., un-pressurizedreaction. When choosing a refractory system factors to be consideredinclude internal temperature, abrasion; erosion and corrosion; desiredheat conservation/limitation of temperature of the external vessel;desired life of the refractory. Examples of appropriate refractorymaterial include high temperature fired ceramics, i.e., aluminum oxide,aluminum nitride, aluminum silicate boron nitride, zirconium phosphate,glass ceramics and high alumina brick containing principally, silica,alumina, chromia and titania. To further protect the gasificationchamber from corrosive gases the chamber is, optionally, partially orfully lined with a protective membrane. Such membranes are known in theart and, as such, a worker skilled in the art would readily be able toidentify appropriate membranes based on the requirements of the systemand, for example, include Sauereisen High Temperature Membrane No 49.

In one embodiment, the refractory is a multilayer design with a highdensity layer on the inside to resist the high temperature, abrasion,erosion and corrosion. Outside the high density material is a lowerdensity material with lower resistance properties but higher insulationfactor. Optionally, outside this layer is a very low density foam boardmaterial with very high insulation factor and can be used because itwill not be exposed to abrasion or erosion. Appropriate materials foruse in a multilayer refractory are well known in the art. In oneembodiment, the multilayer refractory comprises an internally orientedchromia layer; a middle alumina layer and an outer insboard layer. Thewall of the chamber can optionally incorporate supports for therefractory lining or refractory anchors. Appropriate refractory supportsand anchors are known in the art.

Lateral Transfer System

Material is moved through the gasification chamber in order to promotespecific stages of the gasification process (drying, volatilization,char-to-ash conversion). To facilitate control of the gasificationprocess material movement through the gasification chamber can be varied(variable movement) depending on process requirements. This lateralmovement of material through the gasifier is achieved via the use of alateral transfer system comprising one or more lateral transfer units.Movement of reactant material by the lateral transfer system can beoptimized by varying the movement speed, the distance each lateraltransfer unit moves and the sequence in which the plurality of lateraltransfer units are moved in relation to each other. The one or morelateral transfer units can act in coordinated manner or individuallateral transfer units can act independently. In order to facilitatecontrol of the material flow rate and pile height the individual lateraltransfer units can be moved individually, at varying speeds, at varyingmovement distances, at varying frequency of movement.

The individual lateral transfer units comprise a moving element and aguiding element or alignment element. It would be apparent to a workerskilled in the art that the moving element can be equipped withappropriate guide engagement elements. The moving element can include,but is not limited to, a shelf/platform, ram, plow, screw element,carrier ram, conveyor or a belt.

The carrier ram can include a single ram or multiple-finger ram. In oneembodiment, the gasifier design will allow for the use of a single ramor multiple-finger ram. The use of a multiple-finger ram may bepreferably when minimum interference with gas flows is desirable duringoperation of the rams. In the multiple-finger ram design, themultiple-finger ram may be a unitary structure or a structure in whichthe ram fingers are attached to a ram body, with individual ram fingersoptionally being of different widths depending on location. The gapbetween the fingers in the multiple-finger ram design is selected toavoid particles of reactant material from bridging.

In certain embodiments in which the system operates at very hightemperatures, cooling can optionally be provided for the movingelements. In one embodiment using a ram or shelf, cooling within the ramor shelf can be provided. Such cooling could be by fluid (air or water)circulated inside the ram or shelf from outside of the chamber.

In one embodiment, for example as shown in FIGS. 47, 51 and 52, thelateral transfer system can be a movable shelf/platform by whichmaterial is predominantly moved through the gasifier by sitting on topof the shelf/platform. A fraction of material may also be pushed by theleading edge of the movable shelf/platform.

Power to propel the lateral transfer system is provided by a motor anddrive system and is controlled by actuators. The individual lateraltransfer units may optionally by powered by dedicated motor and haveindividual actuators or one or more lateral transfer units may bepowered by a single motor and shared actuators.

The gasification process requires heat. Heat addition can occur directlyby partial oxidation of the feedstock or indirectly by the use of one ormore heat sources know in the art. In one embodiment, the heat sourcecan be circulating hot air. The hot air can be supplied from, forexample, air boxes, air heaters or heat exchangers, all of which areknown in the art. In one embodiment, hot air is provided to each levelby independent air feed and distribution systems. Appropriate air feedand distribution systems are known in the art and include separate airboxes for each level from which hot air can pass through perforations inthe floor of each level to that level or via independently controlledspargers for each floor level.

In one embodiment, each floor level has one or more grooves running thelength of individual steps. The grooves being sized to accommodate hotair and/or steam pipes. The pipes optionally being perforated on theirlower third to half to facilitate the uniform distribution of hot air orsteam over the length of the step. Alternatively, the sparger pipes canbe perforated towards the top of the pipes.

In order to facilitate initial start up of the gasifier, the gasifiercan include access ports sized to accommodate various conventionalburners, for example natural gas, oil/gas or propane burners, topre-heat the chamber. Also, wood/biomass sources, engine exhausts,electric heaters could be used to preheat the chamber.

Process additives may optionally be added to the gasifier to facilitateefficient conversion of feedstock into specified gases. Steam input canbe used to ensure sufficient free oxygen and hydrogen to maximize theconversion of decomposed elements of the input feedstock into productgas and/or non-hazardous compounds. Air input can be used to assist inprocessing chemistry balancing to maximize carbon conversion to a fuelgas (minimize free carbon) and to maintain the optimum processingtemperatures while minimizing the cost of input heat. Optionally, otheradditives may be used to optimize the process and thereby improveemissions.

The invention, therefore, can include one or more process additiveinputs. These include inputs for steam injection and/or air injection.The steam inputs can be strategically located to direct steam into hightemperature regions and into the product gas mass just prior to its exitfrom the gasifier. The air inputs can be strategically located in andaround the gasifier chamber to ensure full coverage of process additivesinto the processing zone. In one embodiment, the process additive inputsare located proximal to the floor of the gasifier.

In one embodiment, the process additive inputs located proximal to thefloor are half-pipe air spargers trenched into the refractory floor.Such air spargers may be designed to facilitate replacement, servicingor modification while minimizing interference with the lateral transferof reactant material. The number, diameter and placement of the airholes in the air spargers can be varied according to system requirementsor lateral transfer system design.

In one embodiment, the gasification chamber can further comprise one ormore ports. These ports can include service ports allow for entry intothe chamber for maintenance and repair. Such ports are known in the artand can include sealable port holes of various sizes. In one embodiment,access to the inside of the gasifier is provided by a manhole at one endwhich can be closed by a sealable refractory lined cover duringoperation. In one embodiment, further access is available by removingone or more air boxes. The gasifier can optionally include a flangedlower section which is connected to a flanged main section of thegasification chamber to facilitate opening of the gasification chamberfor refractory inspection and repair.

The residual solids (ash) after gasification is complete can optionallybe removed from the gasifier and passed to a handling system. Thegasifier may therefore optionally include a controllable solids removalsystem to facilitate solid residue or ash removal. In one embodiment,the controllable solids removal system comprises a ram mechanism to pushthe ash out of the chamber. In one embodiment, the controllable solidsremoval system consists of a system of conveying rams. Optionally, thelength of the ram stroke can be controlled so that the amount ofmaterial fed into a solid residue processing chamber with each strokecan be controlled. In a further embodiment of the invention, thecontrollable solids removal system may comprise of a controllablerotating arm mechanism.

As the material is processed and is moved from region to region in thegasifier the heat generated within the pile can cause melting which willresult in agglomeration of the ash. Agglomerated ash has been shown tocause jamming in drop port type exits. The gasifier therefore canoptionally comprise a means for breaking up ash agglomerates. In oneembodiment, in order to ensure that any agglomerations do not createjamming at the exit from the chamber, a screw conveyor concept is usedto extract the ash from the gasifier. The ram motion will push the ashinto the extractor and the extractor will pull the ash out of thegasifier and feed it into an ash conveyor system. Rotation of theextractor screw breaks up agglomerations before the ash is fed into theconveyor system. This breaking up action can be enhanced by havingserrations on the edge of the extractor screw flights.

A Gas Reformulating System

The invention further comprises a gas reformulating system for thereformulating of gas from the gasifier into reformulated gas of adesired chemical composition. In particular, the reformulating systemuses torch heat from a plasma torch to dissociate the gaseous moleculesand allow their recombination into smaller molecules useful fordownstream application, such as energy generation. The system alsocomprises gas mixing means, process additive units, and a feedbackcontrol system with one or more sensors, one or more process effectorsand computing means to monitor and/or regulate the reformulatingreaction.

The gas reformulating system (GRS) comprises a gas reformulating chamberhaving one or more input gas inlets, one or more reformulated gasoutlets, one or more plasma torches, an oxygen source and controlsystem.

The GRS is capable of converting raw input gas comprising volatilemolecules that can include, for example, carbon monoxide, hydrogen,light hydrocarbons, and carbon dioxide and contaminating particulatematter such as soot and carbon black produced during the gasification ofcarbonaceous feedstock. This GRS provides a sealed environment forcontaining and controlling the process. It uses plasma torch heat todisassociate the volatile molecules into their constituent elements thatthen recombine as a reformulated gas of a desired chemical composition.Process additives such as air and/or oxygen and optionally steam areused to provide the necessary molecular species for recombination. Theplasma torch heat also removes unwanted substances such as paraffins,tars, chlorinated compounds among others, by decomposing and convertingthese unwanted substances to smaller molecules such as H₂ and CO. TheGRS further comprises a control system that regulates the process andthereby enables the process to be optimized.

Downstream of the GRS an induction blower in gaseous communication withthe gas reformulating chamber may be provided to maintain the pressureof the gas reformulating chamber at a pressure of about 0 to −5 mbar.

The GRS is in gaseous communication with the gasifier and, therefore,receives input gas directly from the gasifier. The GRS may furthercomprise a mounting flange or connector for coupling the gasreformulating chamber to the gasifier. To facilitate maintenance orrepair, the GRS may optionally be reversibly coupled to the gasifiersuch that the GRS, if necessary, may be removed.

The gas reformulating chamber has one or more input gas inlets, one ormore reformulated gas outlets, one or more ports for heating devices andone or more inputs for oxygen sources. Input gas enters the plasma-torchheated gas reformulating chamber through one or more input gas inlets orports in the chamber and is optionally blended by gas mixing elements.Ports or inputs are provided through which the oxygen source is injectedinto the gas reformulating chamber. The one or more reformulated gasoutlets or ports enable the reformed reformulated gas to exit the GRSand to be transferred to downstream processes for further refinement orto storage facilities.

The gas reformulating chamber is a chamber with a sufficient internalvolume to accommodate the residence time required for the reformulatingreaction to take place. The gas residence time is the amount of the timethat the gas is required to remain in the gas reformulating chamber toallow the reformulating of input gas to reformulated gas to occur.

Accordingly, in designing the gas reformulating chamber, the requiredgas residence time can be considered. Gas residence time is a functionof the gas reformulating chamber volume and geometry, gas flow rate, thedistance the gas travels and/or the path of the gas through the chamber(i.e., a straight linear passage or a swirling or cyclonic path). Thegas reformulating chamber must, therefore, be shaped and sized in such amanner that the flow dynamics of the gas through the chamber allows foran adequate gas residence time. The gas residence time can be modifiedby the use of air jets that promote a swirling flow of the gas throughthe gas reformulating chamber, such that the passage of the gas isnon-linear and therefore has a longer residence time.

In one embodiment, the gas residence time is about 0.5 to about 2.0seconds. In one embodiment, the gas residence time is about 0.75 toabout 1.5 seconds. In a further embodiment, the gas residence time isabout 1 to about 1.25 seconds. In a still further embodiment, the gasresidence time is about 1.2 seconds.

The gas reformulating chamber may be any shape so long as it allows forthe appropriate residence time to enable sufficient chemicalreformulating of the input gas into reformulated gas. The gasreformulating chamber may be disposed in a variety of positions so longas appropriate mixing of the input gas and residence time is maintained.The gas reformulating chamber can be oriented substantially vertically,substantially horizontally or angularly and have a wide range oflength-to-diameter ratios ranging from about 2:1 to about 6:1. In oneembodiment, the length-to-diameter ratio of the gas reformulatingchamber is 3:1.

In one embodiment, the gas reformulating chamber is a straight,substantially, vertical refractory-lined blind or capped tubular orcylindrical structure having the open bottom (upstream) end in directgaseous communication with the gasifier and one reformulated gas outletproximal to or at the top (downstream) end of the chamber. Optionally,the tubular or cylindrical chamber is formed by capping the top(downstream) end of a refractory-lined tube or cylinder with arefractory-lined lid. In order to facilitate maintenance or repair, thelid may, optionally, be removeably sealed to the tube or cylinder.

The wall of the gas reformulating chamber can be lined with refractorymaterial and/or a water jacket can encapsulate the gas reformulatingchamber for cooling and/or generation of steam or recovery of usabletorch heat. The gas reformulating chamber may have multiple walls, alongwith a cooling mechanism for heat recovery, and the system may alsoinclude heat exchangers for high pressure/high temperature steamproduction, or other heat recovery capability. Optionally, the gasreformulating chamber can include one or more chambers, can bevertically or horizontally oriented, and can have internal components,such as baffles, to promote back mixing and turbulence of the gas.

The gas reformulating chamber may optionally include a collector forsolid particulate matter formed during the reformulating process thatcan be collected and optionally fed into the gasifier for furtherprocessing or the solid residue compartments of a gasification system,such as a solid residue conditioning chamber, for further processing.

The gas reformulating chamber comprises one or more input gas inlets orports to feed input gas into the chamber for processing and one or morereformulated gas outlets or ports to transfer the reformulated gasproduced in the reformulating reactions to downstream processing orstorage. The inlet(s) for input gas is located at or near the first orupstream end. The inlet may comprise an opening or, alternatively, maycomprise a controller to control the flow of input gas into the gasreformulating chamber and/or an injector to inject the input gas intothe gas reformulating chamber.

In one embodiment, the one or more input gas inlets for delivering theinput gas to the gas reformulating chamber can be incorporated in amanner to promote concurrent, countercurrent, radial, tangential, orother feed flow directions. In one embodiment, there is provided asingle input gas inlet with an increasing conical shape. In oneembodiment, the inlet comprises the open first end of the gasreformulating chamber, whereby it is in direct communication with thegasifier.

The attachment site on the gasifier for the GRS may be strategicallylocated to optimize gas flow and/or maximize mixing of the input gasprior to entering the gas reformulating chamber. In one embodiment, thegas reformulating chamber is located at the center of the gasifier,thereby optimizing mixing of the input gas prior to entering the gasreformulating chamber. In one embodiment, the inlet comprises an openinglocated in the closed first (upstream) end of the gas reformulatingchamber. This embodiment uses an input gas inlet port to deliver thevolatiles generated during gasification of carbonaceous feedstock intothe chamber. In one embodiment, the inlet comprises one or more openingsin the wall of the gas reformulating chamber proximal to the first(upstream) end.

In embodiments in which the gas reformulating chamber is connected toone or more gasifiers, one or more inlets in the gas reformulatingchamber may be in direct communication with the one or more gasifierthrough a common opening or may be connected to the gasifier via pipingor via appropriate conduits. One embodiment having this configuration isshown in FIG. 54.

The reformulated gas produced in the reformulating reaction exits thegas reformulating chamber through one or more reformulated gas outletsor ports. One or more outlets or ports for the reformulated gas producedin the gas reformulating chamber are located at or near the second ordownstream end. The outlet may comprise an opening or, alternatively,may comprise a means to control the flow of the reformulated gas out ofthe gas reformulating chamber. In one embodiment, the outlet comprisesthe open second (downstream) end of the gas reformulating chamber. Inone embodiment, the outlet comprises one or more openings located in theclosed second (downstream) end of the gas reformulating chamber. In oneembodiment, the outlet comprises an opening in the wall of the gasreformulating chamber near the second (downstream) end.

The gas reformulating chamber comprises various ports including one ormore ports for heaters, one or more process additive ports, andoptionally one or more access ports, view ports and/or instrumentationports. Heater ports include ports for primary heat sources and optionalsecondary sources. In one embodiment, the gas reformulating chambercomprises one or more ports for mounting plasma torches. In oneembodiment, the gas reformulating chamber comprises two or more portsfor mounting plasma torches heat. In one embodiment, the gasreformulating chamber comprises three or more ports for mounting plasmatorches. In one embodiment, the gas reformulating chamber comprises fouror more ports for mounting plasma torches.

In one embodiment, there is provided two ports for plasma sourcespositioned at diametric locations along the circumference of the gasreformulating chamber. In one embodiment, two ports are provided fortangentially mounting two plasma torches. In one embodiment, the portsfor the tangentially mounted plasma torches are located above the airports or inlets to provide maximum exposure to plasma torch heat.

Optionally, ports for mounting plasma torches may be fitted with asliding mounting mechanism to facilitate the insertion and removal ofthe plasma torch(es) from the gas reformulating chamber and may includean automatic gate valve for sealing the port following retraction of theplasma torch(es).

Optionally, one or more process additive ports or inlets are included toenable process additives, such as carbon dioxide, other hydrocarbons oradditional gases to be injected into the gas reformulating chamber.Optionally, ports or inlets are provided such that reformulated gas notmeeting quality standards may be re-circulated into the gasreformulating chamber for further processing. Ports or inlets may belocated at various angles and/or locations to promote turbulent mixingof the materials within the gas reformulating chamber. One or more portscan be included to allow measurements of process temperatures,pressures, gas composition and other conditions of interest.

In addition, the gas reformulating chamber may further include one ormore ports for secondary torch heat sources to assist in the pre-plasmatorch eating or plasma torch heating of the gas reformulating chamber.Optionally, plugs, covers, valves and/or gates are provided to seal oneor more of the ports or inlets in the gas reformulating chamber.Appropriate plugs, covers, valves and/or gates are known in the art andcan include those that are manually operated or automatic. The ports mayfurther include appropriate seals such as sealing glands.

As noted above, the GRS comprises one or more inputs for one or moreoxygen sources, the oxygen source(s) include, but are not limited to,oxygen, oxygen-enriched air, air, oxidizing medium and steam, thereforethe gas conversion chamber comprises one or more ports for oxygen sourceinputs. In one embodiment, the gas conversion chamber comprises one ormore ports for air and/or oxygen inputs and optionally one or more portsfor steam inputs. In one embodiment, the gas reformulating chambercomprises one or more oxygen source ports. In one embodiment, the gasreformulating chamber comprises two or more oxygen source ports. In oneembodiment, the gas reformulating chamber comprises four or more oxygensource ports. In one embodiment, the gas reformulating chamber comprisessix oxygen source ports. In one embodiment, there is provided nineoxygen source ports arranged in three layers around the circumference ofthe gas reformulating chamber. The oxygen source ports may be in variousarrangements so long as the arrangements provide sufficient mixing ofthe oxygen source with the input gas.

The gas reformulating chamber may further optionally include additionalor supplementary gas mixers at or near the input gas inlet to mix theinput gas such that the input gas is of more uniform composition and/ortemperature and/or to mix the input gas with process additives. In oneembodiment, the mixers comprises two or more air swirl jets at or nearthe input gas inlet which inject a small amount of air into the inputgas and create a swirling motion or turbulence in the input gas streamand thereby mix the input gas by taking advantage of the injected air'svelocity. In one embodiment, the mixer comprises three or more air swirljets at or near the inlet which inject a small amount of air into theinput gas and create a swirling motion or turbulence in the input gasstream and thereby mix the input gas. In one embodiment, the mixercomprises four or more air swirl jets at or near the inlet which injecta small amount of air into the input gas and create a swirling motion orturbulence in the input gas stream and thereby mix the input gas. Thenumber of air swirl jets is designed to provide maximum mixing and swirlbased on the designed air flow and exit velocity, so that the jet couldpenetrate to the center of the chamber.

Baffles may also be used to induce mixing of the input gas by creatingturbulence in the input gas. A baffle is a mechanical obstruction to thenormal flow pattern. Baffles serve to block a section of the combustionchamber cross section, resulting in a rapid increase in flow velocityand a corresponding rapid decrease on the downstream side of the baffle.This generates a high level of turbulence and speeds local mixing.

Baffles may be located at various locations in the gas reformulatingchamber. Baffle arrangements are known in the art and, include but arenot limited, to cross bar baffles, bridge wall baffles and choke ringbaffle arrangements. Accordingly, in one embodiment, the gas mixingmixing comprises baffles. FIGS. 55A and B show embodiments comprisingbaffles.

As noted above, the GRS comprises a oxygen source, the oxygen source caninclude but or not limited to oxygen, oxygen-enriched air, air,oxidizing medium and steam, therefore the gas conversion chambercomprises one or more oxygen source inputs. In one embodiment, the airand/or oxygen and steam inputs comprise high temperature resistanceatomizing nozzles or jets. Appropriate air nozzles are known in the artand can include any commercially available type. The type of nozzlesbeing chosen based on functional requirements, where a type A nozzle isfor changing the direction of air flows for creating the desired swirlsand a type B nozzle is for creating high velocity of air flow to achievecertain penetrations, and maximum mixing.

The nozzles can direct the air to whatever angle is effective for mixingthe gas. In one embodiment, the air jets are positioned tangentially. Inone embodiment, angular blowing is achieved by having a deflector at thetip of the input nozzle, thus allowing the inlet pipes and flanges to besquare with the gas reformulating chamber.

The arrangement of air and/or oxygen inputs is based on the diameter ofgas reformulating chamber, the designed flow and jet velocity, so thatadequate penetration, maximum swirl and mixing can be achieved. Variousarrangements of the oxygen inputs or ports, steam inputs or ports andports for plasma torches which provide sufficient mixing of the inputgas with the injected oxygen and steam and sufficient residence time forthe reformulating reaction to occur are contemplated by the invention.For example, the oxygen inputs or ports, steam inputs or ports and portsfor the plasma torches may be arranged in layers around thecircumference of the gas reformulating chamber. This arrangement allowsfor the tangential and layered injection of plasma gases, oxygen andsteam which results in a swirling motion and adequate mixing of theinput gas with the oxygen and steam and provides a sufficient residencetime for the reformulating reaction to occur. In embodiments in whichthe air and/or oxygen input ports are arranged in layers, the air and/oroxygen jets can optionally be arranged to maximize the mixing effects.

The arrangements of steam inputs or ports is flexible in number, levels,orientations and angle as long as they are located in a position toprovide optimized capabilities to the temperature control. In oneembodiment, the gas reformulating chamber comprises one or more steaminputs or ports. In one embodiment, the gas reformulating chambercomprises two or more steam inputs or ports. The steam inputs or portsmay be in various arrangements so long as the arrangements providesufficient mixing with the input gas. In one embodiment there isprovided two steam input ports arranged in two layers around thecircumference of the gas reformulating chamber and positioned atdiametric locations.

The oxygen and/or steam input ports may also be positioned such thatthey inject oxygen and steam into the gas reformulating chamber at anangle to the interior wall of the gas reformulating chamber whichpromotes turbulence or a swirling of the gases. The angle is chosen toachieve enough jet penetration and maximum mixing based on chamberdiameter and designed air jet flow and velocity.

In one embodiment, the oxygen and/or steam inputs inject air and steamat an angle between about 50-70° from the interior wall of the gasreformulating chamber. In one embodiment, the oxygen and steam inputsinject air and steam at an angle between about 55-65° from the interiorwall of the gas reformulating chamber. In one embodiment, the oxygen andsteam inputs inject oxygen and steam at an about 60° angle from theinterior wall of the gas reformulating chamber.

The air jets can be arranged such that they are all in the same plane,or they can be arranged in sequential planes. The arrangement of airjets is designed to achieve maximum mixing effects. In one embodimentthe air jets are arranged in lower and upper levels. In one embodiment,there are four jets at the lower level and another six jets at upperlevel in which three jets are slightly higher than the other three tocreate cross-jet mixing effects to achieve better mixing.

In one embodiment, the gas reformulating chamber includes oxygen inputs,steam input ports, and ports for plasma torches that are arranged suchthat there is adequate mixing of the gases and steam throughout thechamber. Optionally, the process air can be blown into the chamberangularly so that the air creates a rotation or cyclonic movement of thegases passing through the chamber. The plasma torches may also be angledto provide further rotation of the stream.

In order for the reformulating reaction to occur, the gas reformulatingchamber must be torch heated to a sufficiently high temperature. Aworker skilled in the art could readily determine an adequatetemperature for the reformulating reaction. In one embodiment, thetemperature is about 800° C. to about 1200° C. In one embodiment, thetemperature is about 950° C. to about 1050° C. In one embodiment thetemperature is about 1000° C. to 1200° C. The GRS therefore furthercomprises one or more non-transferred arc plasma torches.Non-transferred arc plasma torches are known in the art and includenon-transferred arc A.C. and D.C. plasma torches. A variety of gaseshave been used with plasma torches including but not limited to air, O₂,N₂, Ar, CH₄, C₂H₂ and C₃H₆. A worker skilled in the art could readilydetermine the type of plasma torches that may be used in the GRS.

In one embodiment, the plasma torch is one or more non-transferred arcA.C. plasma torch(es). In one embodiment, the plasma torch is one ormore non-transferred D.C. plasma torch(es). In one embodiment, theplasma torch is two non-transferred, reverse polarity D.C. plasmatorches. In one embodiment, there are two plasma torches that arepositioned tangentially to create same swirl directions as air and/oroxygen inputs do. In one embodiment, the plasma torch is two 300 kWplasma torches each operating at the (partial) capacity required. In oneembodiment, the gas reformulating apparatus comprises one or more plasmatorch(es). In one embodiment, the gas reformulating apparatus comprisestwo or more plasma torches. In one embodiment, the gas reformulatingapparatus comprises two water cooled, copper electrode, NTAT DC plasmatorches.

In one embodiment, the use of plasma torch heat is minimized bymaximizing the release of torch heat that occurs during thereformulating of carbon or multi-carbon molecules to mainly CO and H₂ byoptimizing the amount of air and/or oxygen injected into the gasreformulating chamber.

A Heat Recycling System

The invention further comprises a system for optimizing the efficiencyof gasifying carbonaceous feedstock by recovering sensible heat from thegasification process and recycling it for use within the system andoptionally for external applications. Various embodiments of the heatrecycling system of the invention are shown in FIGS. 60 to 67.

In one embodiment, the system recycles heat recovered from hot productgas, transferring it back to a gasifier. In particular the systemcomprises means to transfer the hot product gas to a gas-to-air heatexchanger, where the heat from the hot product gas is transferred toambient air to produce heated exchange-air and cooled product gas, andmeans to transfer the heated exchange-air to the exchange-air inletmeans in the gasifier. The heated exchange-air is passed into thegasifier to provide the heat required to drive the gasificationreaction. The heated exchange-air may also optionally be used to preheator pretreat, directly or indirectly, the feedstock to be gasified.

Optionally, the system additionally comprises one or more heat recoverysteam generators to generate steam, which can be used to drive a steamturbine, as a process additive in the gasification reaction, or in someother application. According to one embodiment of the invention, thesystem also comprises a control subsystem comprising sensing elementsfor monitoring operating parameters of the system, and response elementsfor adjusting operating conditions within the system to optimize thegasification process, wherein the response elements adjust the operatingconditions within the system according to the data obtained from thesensing elements, thereby optimizing the efficiency of a gasificationprocess by minimizing energy consumption of the process, while alsomaximizing energy production.

In one embodiment of the present invention, the heat exchanging systemfor transferring heat produced during the gasification process back to agasifier to drive the gasification reaction. In this embodiment, this isaccomplished by heating ambient air with the heat from a hotgasifier/reformulating system in a product gas-to-air heat exchanger toproduce a heated air product (hereinafter referred to as exchange-air),and passing the heated exchange-air produced in the gas-to-air heatexchanger back into the gasifier.

Energy efficiencies are therefore optimized by this system, since therecycling of recovered sensible heat back to the gasification processreduces the amount of energy inputs required from external sources forthe steps of drying, volatilizing and gasifying the feedstock. Therecovered sensible heat may also serve to minimize the amount of plasmaheat required to achieve a desired quality of syngas. Thus, the heatexchange system allows for the efficient gasification of a carbonaceousfeedstock, wherein the heat required for gasification is provided by hotexchange-air, where the exchange-air has been heated using sensible heatrecovered from the hot product gas.

The sensible heat transferred from the product gas to the heatedexchange-air can also be used for external heating applications, as wellas heating applications elsewhere in the gasification process. Forexample, the heated exchange-air can be used directly or indirectly topreheat or pretreat the feedstock to be gasified. In the case of adirect heating/pretreating step, the exchange-air is directly passedthrough the feedstock to heat and/or remove moisture. In the case of anindirect heating/pretreating step, heat is transferred from the heatedexchange-air to oil (or to water to produce steam), wherein the heatedoil (or steam product) is used to heat the wall of a feedstockdryer/preheater. In all cases, the recycling of sensible heat minimizesthe amount of energy inputs required for these heating applications.Thus, the heat recycling system can transfer the heat from the heatedexchange-air to any working fluid of interest. Such working fluids ofinterest include, but are not limited to, oil, water, or another gassuch as nitrogen or carbon dioxide. It is also within the scope of thepresent invention to transfer heat from the converter gas directly tothe working fluid of interest. Where heat is transferred to a workingfluid other than air, an appropriate heat exchanging system is used.

After heat is recovered in the product gas-to-air heat exchanger, theproduct gas, although cooled, typically still contains too much heat toundergo filtering and conditioning steps as are known in the art. Thepresent invention therefore also optionally provides for the furthercooling of the product gas prior to such subsequent filtering andconditioning steps.

Accordingly, the system may optionally include a subsystem forrecovering additional heat from the partially cooled product gas afterit has passed through the gas-to-air heat exchanger. In one embodiment,the system further comprises a heat recovery steam generator, wherebyadditional heat recovered from the product gas is used to convert waterto steam (referred to as exchange-steam).

The exchange-steam produced in the heat recovery steam generator can beused to drive downstream energy generators such as steam turbines and/orbe used in direct-drive turbines and/or can be added to the gasificationprocess. The exchange-steam can also be used in other systems, forexample, for the extraction of oil from tar sands or in local heatingapplications, or it can be supplied to local industrial clients fortheir purposes. In one embodiment, the steam produced using heat fromthe product gas is saturated steam. In another embodiment, the steamproduced using heat from the product gas is superheated steam, which canbe produced either directly though heat exchange between water andproduct gas or between saturated steam and product gas.

Where the system does not include a system for recovering additionalheat from the partially cooled product gas after it has passed throughthe gas-to-air heat exchanger, another system for further cooling theproduct gas prior to conditioning is provided. In one embodiment, thereis provided a dry quench step for further cooling the product gas priorto conditioning. The dry quench step is provided to remove excess heatfrom the product gas to provide a cooled product gas as may be requiredfor the subsequent filtering and conditioning steps. Selection of anappropriate system for further cooling of the product gas prior toconditioning is within the knowledge of a worker skilled in the art. Insome embodiments, the further cooling system is considered to be a partof the gas conditioning system (GCS) described in more detail below.

The control subsystem may also be used to optimize the composition(i.e., heating value) of the product gas produced, and optionally toensure that the system is maintained within safe operational parameters.

The functional requirements for the product gas-to-air heat exchangerare where the hot product gas and the ambient air are each passedthrough the gas-to-air heat exchanger, whereby sensible heat istransferred from the hot product gas to the ambient air to provide theheated exchange-air and the cooled product gas. Different classes ofheat exchangers may be used in the present system, including shell andtube heat exchangers, both of straight, single-pass design and ofU-tube, multiple pass design, as well as plate-type heat exchangers. Theselection of appropriate heat exchangers is within the knowledge of aworker of ordinary skill in the art.

Some particulate matter will be present in the product gas, thus thegas-to-air heat exchanger is designed specifically for a high level ofparticulate loading. The particle size is typically between 0.5 to 100micron. In one embodiment, the heat exchanger is a single pass verticalflow heat exchanger, wherein the product gas flows in the tubes ratherthan on the shell side. In the single pass vertical flow embodiment, theproduct gas flows vertically in a “once through” design, which minimizesareas where build up or erosion from particulate matter could occur.

The product gas velocities should be maintained to be high enough forself-cleaning, while still minimizing erosion. In one embodiment, gasvelocities are between 3000 to 5000 m/min. Under normal flow conditions,gas velocities are from about 3800 m/min to about 4700 m/min.

Due to the significant difference in the ambient air input temperatureand hot product gas, each tube in the gas-to-air heat exchangerpreferably has an individual expansion bellows to avoid tube rupture.Tube rupture may occur where a single tube becomes plugged and istherefore no longer expanding/contracting with the rest of the tubebundle. In those embodiments where the process air pressure is greaterthan the product gas pressure, tube rupture presents a high hazard dueto problems resulting from air entering gas mixture.

In one embodiment of the present invention, the system is runintermittently, i.e., subject to numerous start-up and shut down cyclesas desired. Therefore, it is important that the equipment must bedesigned to withstand repeated thermal expansion and contraction.

In order to minimize the hazard potential from a tube leak, the heatexchange system further comprises one or more individual temperaturetransmitters, for example, at the product gas inlet and product gasoutlet of the gas-to-air heat exchanger, as well as at the exchange-airoutlet. Where the temperature transmitters are associated with theproduct gas outlet of the gas-to-air heat exchanger, these temperaturetransmitters are positioned to detect a temperature rise resulting fromcombustion in the event of having exchange-air leak into the product gasconduit. Detection of such a temperature rise will result in theautomatic shut down of the process air blower so as to eliminate thesource of oxygen. In addition, the heat exchangers are provided, asrequired, with ports for instrumentation, inspection and maintenance, aswell as repair and/or cleaning of the conduits.

In accordance with the present invention, the heated exchange-air may beprovided as required to different regions of the gasifier throughindependent exchange-air feed and distribution systems. The exchange-airfeed and distribution systems comprise exchange-air inlets that allowfor the introduction of heated exchange-air to the gasification region.These inlets are positioned within the converter to distribute theheated exchange-air throughout the converter to initiate and drive thegasification of the feedstock. In one embodiment, the exchange-airinlets comprise perforations located in the floor of the gasifier. Inone embodiment, the exchange-air inlets comprise perforations located inthe walls of the gasifier.

In one embodiment, the exchange-air inlets comprise separate air boxesfor each region from which hot exchange-air can pass throughperforations in the floor of the converter to that region. In oneembodiment, the exchange-air inlets are independently controlledspargers for each region.

The present invention, in addition to the gas-to-air heat exchanger,optionally includes a system for further cooling the product gas priorto a conditioning step. In one embodiment, the system for furthercooling the product gas prior to cleaning and conditioning also providesfor the recovery of additional heat from the product gas. Where recoveryof further sensible heat from the product gas is an objective, the heatis transferred from the product gas to another working fluid, forexample water, oil, or air. The products of such embodiments caninclude, respectively, heated water (or steam), heated oil, oradditional hot air.

In one embodiment, the system of the present invention recovers furthersensible heat from the product gas using a heat exchanger to transferthe heat from the partially cooled product gas to water, therebyproducing either heated water or steam, and a product gas that has beenfurther cooled. In one embodiment, the heat exchanger employed in thisstep is a heat recovery steam generator, which uses the recovered heatto generate exchange-steam. In one embodiment, the water is providedinto the heat exchanger in the form of low temperature steam. In anotherembodiment, the exchange-steam produced is saturated or superheatedsteam.

Steam that is not used within the conversion process or to driverotating process equipment, may be used for other commercial purposes,such as the production of electricity through the use of steam turbines,or in local heating applications or it can be supplied to localindustrial clients for their purposes, or it can be used for improvingthe extraction of oil from the tar sands. The exchange-steam producedmay also be passed through a turbine, thereby driving rotating processequipment, for example, an exchange-air blower or a syngas blower. Theexchange-steam can also be used to indirectly heat feedstock, therebydrying the feedstock prior to gasification in the converter.

In one embodiment, where cooling of different systems or processes isrequired, the excess heat can be removed (and recovered) by a watercooling step. The resulting heated water can be, in turn, used topre-heat the water prior to its use in the HRSG. Heated water streamscome from various sources including, but not limited to, syngas coolingprocesses in the GQCS system, plasma heat source cooling systems. Heatedwater can also be used to preheat oil for various applications.

The heat exchanger for the HRSG is designed with the understanding thatsome particulate matter will be present in the product gas. Again,product gas velocities here are also maintained at a level high enoughfor self-cleaning of the tubes, while minimizing erosion. In oneembodiment where the system for further cooling the product gas prior toconditioning does not include the recovery of additional heat, thecooling step comprises a dry quench step.

Conduit systems are employed to transfer gases from one component of thesystem to another. Accordingly, the system comprises a syngas conduitsystem to transfer the hot product gas to a heat exchanger for recoveryof the product gas sensible heat. The system also comprises anexchange-air conduit system to transfer the heated exchange-air to theconverter, where it is introduced to the converter via exchange-airinlets. The conduit systems typically employ one or more pipes, orlines, through which the gases are transported.

Where the system comprises a heat recovery steam generator, the systemwill also comprise an exchange-steam conduit system to transfer theheated exchange-steam for use in one or more of the applicationspreviously listed. The exchange-steam conduit system may comprisemultiple pipes running in parallel, or a system of branching conduits,where a given branch is designated for a specific application.

The exchange-air conduit system will optionally employ one or more flowregulating devices, flow meters and/or blower, located throughout thesystem to provide a means for controlling the flow rate of theexchange-air. In one embodiment, there are a plurality of exchange-airflow control valves (one for each level) to control the flow ofexchange-air to the gasifier. After each of the control valves, the airis again split to the air boxes for the gasifier and to threedistribution rings around to the reformer, each with various injectionpoints. In one embodiment, there is one exchange-air flow control valveto control the flow of exchange-air to the GRS. In this embodiment, theexchange-air is provided as a process additive.

The exchange-air conduits also optionally comprise means for divertingexchange-air, for example, to venting outlets or to optional additionalheat exchange systems. The flow regulating devices, and/or blowers,and/or diversion means are optionally controlled by a control subsystem,as is discussed in detail below.

The conduit system will also optionally comprise service ports toprovide access to the system for the purpose of carrying out routinemaintenance, as well as repair and/or cleaning of the conduits.

A Gas Conditioning System

The gas conditioning system (GCS) conditions cooled product gas in atwo-stage conditioning process and provides a final conditioned gas thathas an appropriate composition for the desired downstream application.Stage One comprises one or more initial dry/solid phase separation stepsfollowed by Stage Two, comprising one or more further processing steps.In general, in the dry/solid phase separation steps, a substantialproportion of the particulate matter and a large proportion of heavymetal contaminants are removed. In Stage Two, additional amounts ofparticulate matter and heavy metal contaminants as well as optionallyother contaminants present in the gas are removed. Thus, the GCScomprises various components that carry out processing steps, separateparticulate matter, acid gases, and/or heavy metals from the input gasand that, optionally, adjust the humidity and temperature of the gas asit passes through the GCS. The GCS further comprises a control system tocontrol and optimize the overall conditioning process.

The GCS comprises two integrated subsystems: a Converter GC and a SolidResidue GC, both of which carry out Stage One and Stage Two processing.The GCS is also integrated with the residue conditioner and solidresidue produced in Stage One processing by the Converter GC is passedinto the residue conditioner. The Converter GC and the Solid Residue GCcan operate in parallel wherein both subsystems are capable ofindependently conducting both Stage One and Stage two processes, or thetwo subsystems can operate in a convergent manner, wherein they sharesome or all of the components for Stage Two processing.

FIGS. 68, 70 and 72 depict embodiments of the GCS in which the twosubsystems operate in a convergent manner.

In one embodiment, the components of the GCS and the order of each ofthe processing steps are selected to minimize generation of hazardouswaste that must be treated and/or disposed of. The presence and sequenceof the processing steps can be selected, for example, based on thecomposition of the input gas and the composition of the conditioned gasrequired for the selected downstream application.

In one embodiment of the present invention, the amount of hazardouswaste produced by the GCS is less than about 5% of the weight ofcarbonaceous feedstock used. In one embodiment, the amount of hazardouswaste produced is less than about 2% of the weight of carbonaceousfeedstock used. In one embodiment, the amount of hazardous wasteproduced is less than 1% of the weight of carbonaceous feedstock used.In one embodiment, the amount of hazardous waste produced is betweenabout 1 kg and about 5 kg per 1 tonne of carbonaceous feedstock used. Inone embodiment, the amount of hazardous waste produced is between about1 kg and about 3 kg per 1 tonne of carbonaceous feedstock used. In oneembodiment, the amount of hazardous waste produced is between about 1 kgand about 2 kg per 1 tonne of carbonaceous feedstock used.

Stage One of the GCS comprises components for implementing one or moredry or solid phase processing steps that remove at least a portion ofthe heavy metals and a majority of the particulate matter from the inputgas. Suitable solid phase processing steps are known in the art.

For example, heavy metal removal can be achieved using one or more solidphase separation components known in the art. Non-limiting examples ofsuch solid phase separation components include dry injection systems,particle removal units, activated carbon filtration components, andcomponents that allow contact with specialized sorbents, such aszeolites and nanostructures. Selected representative examples aredescribed in additional detail below. As is known in the art, theseparticulate separation components can be used to remove or separateparticulate matter/heavy metals in the solid/dry phase, for example, indry injection processes, activated carbon filtration, dry scrubbing,various particle removal processing steps and other dry or solid phaseprocessing steps known in the art.

In one embodiment of the present invention, Stage One of the ConverterGC comprises a dry injection system and one or more particle removalunits and Stage One of the Solid Residue GC comprises one or moreparticle removal units.

Selection of the appropriate Stage One processing steps can be readilydetermined by one skilled in the art based on, for example, thecomposition of the input gas, the temperature of the input gas, thedesired composition of the final conditioned gas, the end use of thecomposition gas, as well as cost considerations and equipmentavailability. Stage One of the GCS can optionally comprise one or moregas coolers if required.

As noted above, Stage One of the GCS provides for removal of themajority of the particulate matter and at least a portion of the heavymetal contaminants present in the input gas. In one embodiment, at leastabout 70% of the particulate matter present in the input gas is removedin Stage One. In one embodiment, at least about 80% of the particulatematter present in the input gas is removed in Stage One. In oneembodiment, at least about 90% of the particulate matter present in theinput gas is removed in Stage One. In one embodiment, at least about 95%of the particulate matter present in the input gas is removed in StageOne. In one embodiment, at least about 98% of the particulate matterpresent in the input gas is removed in Stage One. In one embodiment, atleast about 99% of the particulate matter present in the input gas isremoved in Stage One. In one embodiment, 99.5% of the particulate matterpresent in the input gas is removed in Stage One.

In one embodiment, at least about 50% of the heavy metal contaminantspresent in the input gas are removed in Stage One. In one embodiment, atleast about 60% of the heavy metal contaminants present in the input gasare removed in Stage One. In one embodiment, at least about 70% of theheavy metal contaminants present in the input gas are removed in StageOne. In one embodiment, at least about 80% of the heavy metalcontaminants present in the input gas are removed in Stage One. In oneembodiment, about 90% of the heavy metal contaminants present in theinput gas are removed in Stage One.

Dry injection processes are known in the art and generally utilize acalculated amount of a suitable sorbent which is injected in the gasstream with enough residence time so that fine heavy metal particles andfumes can adsorb on the surface of the sorbent. Heavy metals adsorbed onsorbent can be captured by a particle removal such as those describedbelow, which removes heavy metals/particulate matter in the dry/solidphase and prevent it from moving through the GCS along with the inputgas.

Examples of suitable sorbents include, but are not limited to, activatedcarbon; promoted-activated carbon impregnated with iodine, sulphur, orother species; feldspar; lime; zinc-based sorbents; sodium-basedsorbents; metal oxide based sorbents; and other physical and chemicaladsorbents known in the art that are capable of effectively removingheavy metals such as mercury, arsenic, selenium and the like. Thesorbents may be a mesh size varying between a maximum size of about a 60mesh size and minimum size of about a 325 mesh size.

Injection is generally through a sorbent input, such as a port, nozzleor tube, and can be achieved by gravity, locked hopper, or screwconveyor. The present invention also contemplates that the sorbent canbe provided within pipes that make up the GCS, for example in a pipeleading to a particle removal means, to be mixed with the input gas asit passes through the pipe. Other methods known in the art are alsoincluded. The GCS can comprise multiple sorbent inputs or a singlesorbent input.

The sorbents can be stored in one or more holding containers from whichthe sorbent(s) are delivered to the input(s). The sorbent holdingcontainers can be part of the GCS or can be external to the GCS.

As noted above, various combinations of sorbents can be injected intothe input gas by dry injection and suitable combinations can be readilydetermined by one of skill in the art based on, for example, thecomposition of the input gas. In one embodiment, feldspar is injectedinto the input gas. In one embodiment, activated carbon is injected intothe input gas. In one embodiment, feldspar is used as a pre-coat for theparticle removal means. In one embodiment, activated carbon is injectedinto the input gas, and the particle removal means are precoated withfeldspar. In one embodiment, feldspar is continuously injected into thesystem.

In one embodiment, the GCS of the present invention includes one or moreparticle removal units which act to remove particulate matter from theinput gas. Particle removal means can also remove heavy metals, such aselemental mercury, from the input gas. In embodiments where dryinjection is employed in the GCS, the one or more particle removal unitsalso serve to remove contaminant-laden sorbents from the input gas.Examples of suitable particle removal units include, but are not limitedto, cyclone separators or filters, high temperature ceramic filters,moving bed granular filters, baghouse filters, and electrostaticprecipitators (ESP).

As is known in the art, the choice of particle removal unit will dependon, for example, the temperature of the input gas, the size of theparticulate matter to be removed, and, when applicable, the type ofsorbent injected into the gas stream. Suitable particle removal unitscan be readily selected by one of skill in the art. In one embodiment ofthe present invention, Stage One of the GCS comprises one or moreparticle removal units selected from a cyclone filter, a hightemperature ceramic filter and a baghouse filter. In one embodiment,each of Stage One of the Converter GC and the Solid residue GC comprisea baghouse.

Cloth collectors such as baghouse filters can collect particles of asize down to about 0.01 microns, depending on the type of filteremployed. Baghouse filters are typically fabric filters, cellulosefilters or organic polymer-based filters. Other examples of filters thatcan be used in a baghouse context include, but are not limited to, linedand unlined fiberglass bags, Teflon lined bags and P84 basalt bags.Suitable filters can be readily selected by those of skill in the artbased on considerations such as, one or more of the temperature of theinput gas, the moisture levels in the baghouse and in the input gas, theelectrostatic nature of the particles in the input gas, acid and/oralkali chemical resistance of the filter, the ability of the filter torelease the filter cake, filter permeability and the size of theparticles.

In one embodiment of the present invention, the GCS comprises a baghousefilter and is configured such that the temperature of the gas enteringthe baghouse is between about 180° C. and about 280° C. As is known inthe art, operating a baghouse filter at a higher temperature candecrease the risk of tars in the input gas plugging the filters andreducing efficiencies. Higher temperatures can reduce the efficiency ofparticle removal by the baghouse filters, for example, increasing theoperating temperature from 200° C. to 260° C. decreases particle removalefficiency from 99.9% to 99.5%. Thus, when higher operating temperaturesare selected for a baghouse filter comprised by the GCS, the GCS cancomprise additional downstream components, either in Stage One or StageTwo, to capture remaining particulates. For example, wet scrubbers andactivated carbon beads can be included for removal of particulates inaddition to other contaminants. In one embodiment of the presentinvention in which the GCS comprises a baghouse filter, the GCS isconfigured such that the temperature of the gas entering the baghouse isbetween about 250° C. and about 260° C. In another embodiment in whichthe GCS comprises a baghouse filter, the GCS is configured such that thetemperature of the gas entering the baghouse is between about 190° C.and about 210° C.

In one embodiment, a gas cooling system may be used to cool the inputgas before it enters the particle removal unit. For example, as is knownin the art, cooling of the input gas may be of particular importancewhen a baghouse type filter is used for particulate removal, sincebaghouse type filters often cannot withstand extremely hightemperatures.

In accordance with one embodiment of the present invention, the GCS isconfigured to process input gas for which the temperature has beenreduced by passing the input gas through a gas cooler prior to entryinto the GCS. In another embodiment of the present invention, the GCScomprises one or more gas coolers for reducing the temperature of theinput gas prior to entry into Stage One processing. Suitable gas coolersfor incorporation into the GCS are known in the art and include, but arenot limited to, dry quenchers, evaporative cooling towers, gas coolers,chillers, recuperators, heat exchangers, indirect air to gas heatexchangers, and heat recovery steam generators (HRSGs). In oneembodiment, the GCS comprises a heat exchanger and/or a dry quencher.

In one embodiment, the GCS incorporates an evaporative cooling tower inStage One to cool the temperature of the syngas from about 740° C. toabout 150-200° C., for example, by adiabatic saturation, which involvesdirect injection of water into the gas stream in a controlled manner.The evaporating cooling process is a dry quench process, and can bemonitored to ensure that the cooled gas is not wet, i.e. that therelative humidity of the cooled gas is still below 100% at the cooledtemperature.

Suitable residue conditioning chambers for incorporation into the GCSare described in detail below. The residue conditioning chamber can beshared with the converter of the facility, or the GCS may include adedicated residue conditioning chamber.

FIG. 78A depicts the configuration in one embodiment of the presentinvention for a solid residue conditioner, a converter and a Stage Onebaghouse of the GCS.

Stage Two of the GCS comprises one or more components for implementingfurther processing steps that remove additional amounts of particulatematter and heavy metal contaminants, and other contaminants present inthe input gas. Stage Two processes can include dry phase separationsteps as described for Stage One and/or other separation steps,including wet processing steps. Non-limiting examples of otherprocessing steps that may be implemented in Stage Two include processesthat remove acid gases, heavy metals and particulate matter, and othercontaminants such as dioxin, furan, CO₂, and ammonia. As is known in theart, various components can be used to carry out these processes,including various wet scrubbers (such as venturi scrubbers and impinjetscrubbers), chloride guard beds, wet ESP and the like. Stage Two canalso include cooling units and/or humidity controllers, as well as gasmoving units for ensuring that the input gas moves through the system.Examples of Stage Two processing steps, other than those alreadydescribed in Stage One, are described below.

Input gases to be processed in the GCS include as contaminants acidgases such as HCl and H₂S. The concentrations of these acid gases insyngas can range from about 0.05 to about 0.5% for HCl, and from about100 ppm to about 1000 ppm for H₂S, depending on the carbonaceousfeedstock used in the gasification process. In one embodiment, the GCSis configured to process input gas comprising about 0.178% of HCl andabout 666 ppm (0.07%) of H₂S. In one embodiment, the GCS is configuredsuch that the conditioned gas exiting the GCS contains between about 20ppm and about 5 ppm HCl and between about 30 ppm and about 20 ppm H₂S.

Acid gas removal or separation can be achieved by dry scrubbing or wetscrubbing processes. In one embodiment, Stage Two of the GCS comprises awet scrubbing process to remove acid gases.

In addition to dry and wet scrubbing processes as described above, anumber of processing steps are known in the art for removing HCl vaporfrom gases. Non-limiting examples of such processing steps include:adsorption of the HCl on activated carbon or alumina, reaction withalkali or alkaline earth carbonates or oxides, the use of chlorideguards, and the use of high temperature sorbents such as alkali andalkaline earth compounds, shortite (Na₂CO₃.2CaCO₃) and trona(Na₂CO₃.NaHCO₃.2H₂O), eutectic melts of Li₂CO₃ and Na₂CO₃, and flue gassorbents such as alkalized alumina. In one embodiment, Stage Two of theGCS comprises an HCl scrubber for removal of HCl from the input gasusing alkaline solution.

H₂S may be removed from the input gas using various processes known inthe art including wet and dry scrubbing processes as outlined above.Suitable methods include for example, wet absorption with NaOH ortriazine, dry adsorption with Sufatreat, biological processes such asthe use of Thiopaq® scrubbers, or selective oxidation, including liquidredox (Low CAT). Physical solvent processes can also be used to separateH₂S from the input gas. Non-limiting examples of such physical solventthat can be used include polyethylene glycol derivatives such asSelexol®; fluor solvents such as anhydrous propylene carbonate; methanolas used in a Rectisol process. In one embodiment, Stage two of the GCScomprises a Thiopaq® scrubber for removal of the H₂S from the input gas.

Processes and particle removal units suitable for use in Stage Oneprocesses can also be used in Stage Two processes and have beendescribed above. Activated carbon filtration employing an activatedcarbon filter bed or a fluidized bed can also be used as remove heavymetals and/or particulate matter from the input gas. In one embodiment,the GCS comprises a carbon bed filter or mercury polisher as a particleremoval unit in Stage Two.

As is known in the art, at a relative humidity (R.H.) of greater than50%, water will start to adsorb on the carbon of the carbon bed filterand obstruct diffusion, which affects removal performance. This can becorrected, however, by increasing bed depth. Carbon bed filters can alsobe used at higher relative humidities, for example between ˜70% R.H and100% R.H., when lower performance is acceptable as the performanceeffect is only seen when the desired final content of mercury in theconditioned gas is in the 0.001 to 0.01 ug/Nm3 mercury range. Forexample, when mercury concentrations of about 19 ug/Nm3 are acceptable,the higher R.H. ranges can be used.

In one embodiment, the GCS comprises an activated carbon filter with 7-8inches of Water Column pressure drop to achieve about 99.8% removal ofmercury.

In embodiments where the input gas comprises dioxin and furan, the GCScan optionally comprise an activated carbon injection step which willresult in the dioxin and furan present in the gas being adsorbed to thecarbon surface. The carbon can then be removed by a suitable particleremoval unit. In one embodiment, the GCS comprises a spray dryerabsorber that decreases the residence time at the relevant temperaturerange to minimise the possibility of dioxin/furan formation.

The GCS can optionally include components for the removal of carbondioxide and/or ammonia if removal of these compounds is required.Suitable components are known in the art. As is also known in the art,ammonia can be removed from the input gas during the HCl scrubbing step.

FIGS. 69, 71, 73, 74 and 75 depict various non-limiting options forStage One and Stage Two processing steps for the GCS in one embodimentof the present invention.

Cooling units and/or humidity controllers can optionally be included inthe GCS as part of Stage One (as described above) or Stage Two. Suitablecomponents are known in the art and include, but are not limited to,evaporative cooling towers, gas coolers, chillers, recuperators, heatexchangers, indirect air to gas heat exchangers, and heat recovery steamgenerators (HRSGs). Recuperators and HRSGs can be used to cool the gaswhile utilizing the heat instead of dissipating it as is done byevaporative cooling towers, gas coolers, and chillers.

Demisters/reheaters may be incorporated in the GCS for moisture removaland/or prevention of condensation as is known in the art. Heatexchangers can be included to reheat the final conditioned gas to therequired temperature or relative humidity for the desired downstreamapplication. A compressor can also optionally be included to compressthe final conditioned gas to the required pressures for the desireddownstream application.

In one embodiment, a gas cooler may be included in Stage Two of the GCS.The gas cooler (water cooled) functions to cool input gas that ispressurized through a gas moving unit (see below) and concomitantlyheated. In one embodiment, the gas cooler cools the gas to about 35° C.

In one embodiment, the GCS comprises a humidity controller. The humiditycontroller functions to ensure that the humidity of the output gas isappropriate for the downstream application desired. For example, ahumidity controller may include a chiller to cool the gas stream andthus condense some water out of the gas stream. This water can beremoved by a gas/liquid separator. In one embodiment, the GCS comprisesa humidity controller for treatment of the conditioned gas to provide ahumidity of about 80% at 26° C. In one embodiment, the GCS is configuredto first cool the conditioned gas to approximately 26° C. and thenreheat the gas to 40° C. The conditioned gas may then be stored.

In one embodiment, the GCS includes one or more gas moving units whichsupply a driving force for the gas throughout the GCS and move the inputgas from the exit of the gasification system up to exit of the GCS.

Suitable gas moving units are known in the art and include, for example,process gas blowers, pressure blowers, vacuum pumps, positivedisplacement rotary blowers, reciprocating compressors, and rotary screwcompressors and the like. In one embodiment, the GCS comprises a processgas blower as a gas moving unit. In one embodiment, the GCS comprises agas moving unit that additionally pressurizes the gas passing throughthe blower.

The optimal placement of the gas moving unit within the GCS can bedetermined by one of skill in the art. In one embodiment, the gas movingunit is located so as to increase the efficiency of one or more of theprocessing steps of the GCS. For example, in one embodiment, the gasmoving unit is located upstream of a heavy metal polisher such as amercury polisher to optimise mercury removal, as this occurs mostefficiently under pressure, and can also allow a reduced size mercurypolisher vessel to be used.

A Residue Conditioning System

The invention further comprises a system for the conversion of residualmatter from the converter into an inert slag product and a gas having aheating value. In particular, the system comprises a refractory-linedresidue conditioning chamber comprising a residue inlet, a gas outlet, aslag outlet, a plasma heat source, and a control subsystem formonitoring operating parameters and adjusting operating conditionswithin the system to optimize the conversion reaction. The plasma heatcauses the residue to melt, and converts unreacted carbon present in theresidue to a residue gas, which exits the chamber through the gasoutlet, and optionally into a gas conditioning subsystem for cooling andconditioning as required for downstream considerations.

Various embodiments of the residue conditioning system of the inventionare shown in FIGS. 76 to 85.

The chamber may also optionally comprise one or more inlets forintroducing air (or other oxygen containing additives) into the residueconditioning chamber to control the conditioning process. The chambermay also optionally comprise one or more additive inlets for introducingadditives to control the composition of the resulting slag product.

The residue conditioning system of the present invention comprises aresidue conditioning chamber which is adapted to i) input the residue tobe conditioned, ii) input heat and condition the residue to form amolten slag material and a gaseous product having a heating value, andiii) output the molten slag and gaseous product. Accordingly, theresidue conditioning chamber is a refractory-lined chamber comprising aresidue inlet, a gas outlet, a slag outlet, and a plasma heat sourceport. The residue conditioning chamber further optionally includes oneor more air and/or steam inlets.

The residue conditioning chamber is designed to ensure that the residueconditioning process is carried out efficiently and completely, in orderto use a minimum amount of energy to effect complete conditioning of theresidue. Accordingly, factors such as efficient heat transfer, adequateheat temperatures, residence time, molten slag flow, input residuevolume and composition, and size and insulation of the chamber are takeninto account when designing the residue conditioning chamber. Thechamber is also designed to ensure that the residue conditioning processis carried out in a safe manner. Accordingly, the system is designed toisolate the residue conditioning environment from the externalenvironment.

The residue conditioning chamber is provided with a plasma heat sourcethat meets the required temperature for heating the residue to levelsrequired to convert any remaining volatiles and carbon to a gaseousproduct having a heating value and to melt and homogenize the residue toprovide a molten slag at a temperature sufficient to flow out of thechamber. The chamber is also designed to ensure highly efficient heattransfer between the plasma gases and the residue, to minimize theamount of sensible heat that is lost via the product gas. Therefore, thetype of plasma heat source used, as well as the position andorientation, of the plasma heating means are additional factors to beconsidered in the design of the residue conditioning chamber.

The residue conditioning chamber is also designed to ensure that theresidue residence time is sufficient to bring the residue up to anadequate temperature for melting and homogenization, and to fullyconvert the carbon to the gaseous product. Accordingly, the chamber isprovided with a reservoir in which the residue accumulates while beingheated by the plasma heat source. The reservoir also allows mixing ofthe solid and molten materials during the conditioning process.Sufficient residence time and adequate mixing ensures that theconditioning process is completely carried out, and that the resultingslag and gaseous products have the desired composition.

The chamber is designed for continuous or intermittent output of themolten slag material. Continuous slag removal allows the conditioningprocess to be carried out on a continual basis, wherein the residue tobe conditioned may be continuously input and processed by the plasmaheat, without interruption for periodic slag removal.

In one embodiment, continuous slag exhaust is achieved by using areservoir bounded on one side by a weir that allows the slag pool toaccumulate until it exceeds a certain level, at which point the moltenslag runs over the weir and out of the chamber. In this embodiment, theresidue drops through a residue inlet located at the top of theconditioning chamber into a reservoir, where it is conditioned by aplasma torch plume. The molten materials are held in the reservoir by aweir until the pool reaches the top of the weir. Thereafter, asadditional residue enters the system and is conditioned, a correspondingamount of molten material overflows the weir and out of the chamberthrough a slag outlet.

Where the residue being conditioned contains a significant amount ofmetal, and the residue conditioning chamber comprises a reservoirbounded by a weir, the metals, due to their higher melting temperatureand density, typically accumulate in the reservoir until such time asthey are removed. Accordingly, in one embodiment of the presentinvention, the reservoir is optionally provided with a metal tap port,whereby the tap port is plugged with a soft refractory paste which maybe periodically removed using the heat from an oxygen lance. Once thetap port has been opened and the chamber temperature has been raisedsufficiently to melt the accumulated metals, the molten metals aretapped off from the bottom of the reservoir.

In one embodiment, the reservoir itself may also be provided with a slagoutlet adapted for continuous exhaust of the molten slag. In oneembodiment, the reservoir may also provide for intermittent slagremoval, wherein the reservoir is designed to allow the accumulation ofmolten materials until the conditioning process is complete, at whichpoint the molten slag is exhausted.

Due to the very high temperatures needed to melt the residue, andparticularly to melt any metals that may be present, the residueconditioning chamber wall is lined with a refractory material that willbe subjected to very severe operational demands. The selection ofappropriate materials for the design of a residue conditioning chamberis made according to a number of criteria, such as the operatingtemperature that will be achieved during typical residue conditioningprocesses, resistance to thermal shock, and resistance to abrasion anderosion/corrosion due to the molten slag and/or hot gases that aregenerated during the conditioning process.

The inner refractory is selected to provide an inner lining having veryhigh resistance to corrosion and erosion, particularly at the slagwaterline, in addition to resistance to the high operating temperatures.The porosity and slag wetting capability of the inner refractorymaterial must be considered to ensure that the refractory materialselected will be resistant to penetration of the molten slag into thehot face. The materials are also selected such that secondary reactionsof the refractory material with hydrogen are minimized, thereby avoidinga possible loss of integrity in the refractory and contamination of theproduct gas.

The residue conditioning chamber is typically manufactured with multiplelayers of materials as are appropriate. For example, the outer layer, orshell, of the chamber is typically steel. Moreover, it may be beneficialto provide one or more insulating layers between the inner refractorylayer and the outer steel shell to reduce the temperature of the steelcasing. Where a second layer (for example, an insulating firebricklayer) is provided, it may also be necessary to select a material thatdoes not react with hydrogen. An insulating board around the outersurface of the slag reservoir may also be provided to reduce thetemperature of the steel casing. When room for expansion of therefractory without cracking is required, a compressible material, suchas a ceramic blanket, can be used against the steel shell. Theinsulating materials are selected to provide a shell temperature highenough to avoid acid gas condensation if such an issue is relevant, butnot so high as to compromise the integrity of the outer shell.

The refractory material can therefore be one, or a combination of,conventional refractory materials known in the art which are suitablefor use in a chamber for extremely high temperature (e.g., a temperatureof about 1100° C. to 1800° C.) non-pressurized reaction. Examples ofsuch refractory materials include, but are not limited to, hightemperature fired ceramics (such as aluminum oxide, aluminum nitride,aluminum silicate, boron nitride, chromic oxide, zirconium phosphate),glass ceramics and high alumina brick containing principally, silica,alumina and titania.

Due to the severe operating conditions, it is anticipated that thereservoir refractory will require periodic maintenance. Accordingly, inone embodiment, the residue conditioning chamber is provided inseparable upper and lower portions, wherein the chamber lower portion(where the reservoir is located) is removable from the chamber upperportion. In one embodiment, the chamber is suspended from a supportstructure such that the lower portion can be dropped away from the upperportion to facilitate maintenance. This embodiment provides for removingthe lower portion without disturbing any connections between the chamberupper portion and upstream or downstream components of the system.

The residue conditioning chamber may also include one or more ports toaccommodate additional structural elements or instruments that mayoptionally be required. The chamber may also include service ports toallow for entry or access into the chamber for scrubbing/cleaning,maintenance, and repair. Such ports are known in the art and can includesealable port holes of various sizes. In one embodiment, the port may bea viewport that optionally includes a closed circuit television tomaintain operator full visibility of aspects of the residue processing,including monitoring of the slag outlet for formation of blockages.

In one embodiment, the residue conditioning chamber may be tubular inshape. This embodiment comprises a torch mounting port, a residue inlet,a reservoir bounded on one side by a weir, a slag outlet, and a metaltap port.

The system comprises a residue input means in association with theresidue inlet of the conditioning chamber. The residue inlet is adaptedto receive the residue into the residue conditioning chamber. Theresidue input means conveys the residue from a source of the residuematerial to the inlet of the conditioning chamber.

Residue material entering the chamber may come from one or multiplesources. Sources of the residue may include, but are not limited to, alow temperature or high temperature gasifier, a hopper in which theresidue is stored, or upstream gas conditioning systems, for example, abaghouse filter.

Where the residue to be conditioned is provided in more than one inputstream, or from more than one source, the different streams may each bepassed into the conditioning chamber through a dedicated residue inlet,or they may be combined prior to introduction into the residueconditioning chamber. In the latter embodiment, there is provided oneresidue inlet through which all residues are provided. Accordingly, thechamber may comprise a common inlet or multiple inlets to cater to anyphysical characteristics of the input residue material.

The source of the residue may be provided in direct communication withthe conditioning chamber, i.e., each residue input is fed directly fromthe source into the residue conditioning chamber. Alternatively, thesource may be provided in indirect communication with the residueconditioning chamber, wherein the residue inputs are conveyed from thesource into the residue conditioning chamber via a system of conveyormeans.

Where the residue conditioning chamber is indirectly connected to thesource of the residue, the residue input means comprises one or moremeans for conveying the residue from the source into the residueconditioning chamber. For example, the residue input means may include asingle screw conveyor or a series of screw conveyors.

In embodiments wherein the residue conditioning chamber is directlyconnected to the source of the residue, the residue source and residueconditioning chamber employed may be the same as those of the indirectlyconnected embodiment, with the exception that the source of residuecommunicates directly with conditioning chamber, without the need for anintermediate conveying means. In this arrangement the residue passesdirectly from the source of residue into the adjoining (and integral)residue conditioning chamber. In such a “contiguous” embodiment, theresidue may be conveyed actively or passively (i.e., by gravity) fromthe residue source into the chamber.

In directly connected (or contiguous) embodiments where the residue isactively conveyed into the residue conditioning chamber, the residueinput means is typically located within the residue source. Suchconveyance means may include screw conveyors, rotating arms, rotatingchains, traveling grates and pusher rams.

The residue input means optionally include a control mechanism such thatthe input rate of the residue can be controlled to ensure optimalmelting and homogenization of the residue material.

In one embodiment of the invention, solid process additives are added tothe residue to be conditioned in order to adjust the composition of theslag product. These solid process additives may be added to the residueprior to introduction into the residue conditioning chamber, or they maybe added directly to the residue conditioning chamber through adedicated additive inlet. In one embodiment, the solid process additiveis added directly to the conditioning chamber via a dedicated additivefeed inlet. In one embodiment, the additive is introduced to the residueprior to introduction to the conditioning chamber.

Where the residue conditioning system is associated with a carbonaceousfeedstock gasification process, it is also possible to add the solidprocess additive to the feedstock prior to gasification.

The residue conditioning system employs one or more plasma heatingsources to convert the residue material produced by the upstreamprocesses. The plasma heat sources may be movable, fixed or acombination thereof.

The plasma heat sources may comprise a variety of commercially availableplasma torches develop suitably high flame temperatures for sustainedperiods at the point of application. In general, such plasma torches areavailable in sizes from about 100 kW to over 6 MW in output power. Theplasma torch can employ one or a combination of suitable working gases.Examples of suitable working gases include, but are not limited to,argon, helium, neon, hydrogen, methane, ammonia, carbon monoxide,oxygen, nitrogen, and carbon dioxide. In one embodiment of the presentinvention, the plasma heating means is continuously operating so as toproduce a temperature in excess of about 900° C. to about 1800° C. asrequired for converting the residue material to the inert slag product.

In this respect, a number of alternative plasma technologies aresuitable for use in the present system. For example, it is understoodthat transferred arc and non-transferred arc torches (both AC and DC),using appropriately selected electrode materials, may be employed. It isalso understood that inductively coupled plasma torches (ICP) may alsobe employed. Selection of an appropriate plasma heat source is withinthe ordinary skills of a worker in the art.

The use of transferred arc torches instead of non-transferred arctorches may improve the efficiency of the residue conditioning processdue to their higher electrical to thermal efficiency, as well as thehigher heat transfer efficiency between the hot plasma gases and thematerial being melted because the arc passes directly through the melt.Where transferred arc torches are used, it is necessary to ensure thatthe conditioning chamber is electrically isolated since the chamberouter shell will be connected to the negative of the power supply. Inone embodiment, the plasma heat source is a DC non-transferred arctorch.

In one embodiment of the present invention, the residue conditioningsystem comprises one or more plasma heat sources positioned to optimizethe conversion of the residue material to inert slag. The position ofthe plasma heat source(s) is selected according to the design of theresidue conditioning chamber. For example, where a single plasma heatsource is employed, the plasma heat source may be mounted in the top ofthe chamber and disposed in a position relative to the slag poolcollecting at the bottom of the chamber to ensure sufficient heatexposure to melt the residue material and force the slag to flow. In oneembodiment, the plasma heat source is a plasma torch vertically mountedin the top of the chamber.

All plasma heat sources are controllable for power and optionally (wheremovable heat sources are used) position. In one embodiment, the plasmaheat rate is varied to accommodate varying residue input rate. Theplasma heat rate can also be varied to accommodate varying residuemelting temperature properties.

The plasma heat sources may be operated on a continuous ornon-continuous basis at the discretion of the operator to accommodatevarying residue input rate and melting temperature properties.

The residue being conditioned will typically contain a proportion ofunreacted or unconverted carbon. Accordingly, air and/or steam mayoptionally be added to the residue conditioning chamber to ensurecomplete conversion of the carbon, as required by the varying carboncontent of the residue material being conditioned. Since the carbonreacts with oxygen in an exothermic reaction, air inputs may also beused and adjusted to maintain optimum processing temperatures whileminimizing the cost of plasma heat required in the conditioning process.As such, the amount of air injection is maintained to ensure the maximumconversion of carbon to carbon monoxide with the minimum plasma heatrequirement to carry out the process.

If the temperature within the conditioning chamber is too high and/orthe gaseous product of the conditioning process has a high carbonparticle (soot) content, steam can be injected to control thetemperature and/or convert the solid carbon to carbon monoxide andhydrogen.

The chamber, therefore, can include one or more air input ports for airinjection, and optionally one or more steam input ports for steaminjection. The air and steam input ports are strategically located inand around the residue conditioning chamber to ensure full coverage ofthe air and steam inputs into the chamber.

The system of the present invention comprises a slag output inassociation with the conditioning chamber. The slag output includes anoutlet on the residue conditioning chamber through which molten slag isexhausted. The outlet is typically located at or near the bottom of thechamber to facilitate the gravity flow of the molten slag pool out ofthe chamber. The slag output also includes a slag cooling subsystem tofacilitate the cooling of the molten slag to it solid form.

The molten slag can be output from the chamber intermittently, e.g.,through a batch pour or periodic exhausting at the end of a processingperiod. The molten slag can also be output in a continuous mannerthroughout the full duration of processing. The molten slag from eithermethod can be cooled and collected in a variety of ways that will beapparent to a person skilled in the art, to form a dense, non-leachable,solid slag. The slag output means may further be adapted to minimizeheating requirements and to avoid contact of the product gas withexternal air by keeping the residue conditioning chamber sealed.According to the present invention, as the residue is conditioned by theplasma heat, the resulting molten slag accumulates in a reservoir. Asdiscussed previously, in one embodiment of the invention, the moltenslag is extracted in a continuous manner, i.e., as the volume of moltenslag in the reservoir increases, it passes over a weir and exits theconditioning chamber through an outlet.

In one embodiment of the residue conditioning chamber, the molten slagis exhausted through an S-trap outlet. In this embodiment, the slagoutput means may optionally comprise a burner or other heating meanslocated at or near the outlet in order to maintain the temperature ofthe molten slag at the outlet high enough to ensure that the outletremains open through the complete slag extraction period. Thisembodiment also ensures that the level of the slag pool does not gobelow a predetermined level, thereby keeping the melt environment sealedto avoid gaseous contact with the external environment.

Continuous pour embodiments are particularly suitable for systems thatare designed to operate on a continuous basis, for example, where theresidue conditioning system is provided in association with a continuousfeedstock gasification facility.

In one embodiment, the molten slag accumulates in a reservoir until thereservoir is periodically emptied. In such an embodiment, the reservoirmay be emptied by a tipping mechanism, or through an outlet in thereservoir as may be provided to controllably exhaust the molten slag.

In one embodiment a mechanism is provided to controllably exhaust themolten slag from a reservoir by a tipping mechanism. In this embodiment,the residue conditioning chamber has a tiltable crucible comprisingreservoir, a spout, a counterweight and a lever arm provided as amechanism for tilting the crucible.

In different embodiments, there are different design options that may beprovided for controlled exhaust of the molten slag through anappropriately adapted outlet in the reservoir or chamber. The moltenslag exhaust may be controlled to ensure that the level of the moltenslag is not allowed to reach below the top of the outlet, so that gasesfrom the external atmosphere do not enter the interior melt region.

In one embodiment, a reservoir or chamber has an outlet in a side wallnear the bottom of the reservoir/chamber. The outlet is surrounded by aninduction heater enclosed in the refractory that can control thetemperature of the refractory in the region surrounding the outlet.Increasing the temperature sufficiently to maintain the slag in themolten state allows the slag to flow though the outlet. When the levelof the slag pool reaches the desired level, the induction heater isturned off, and the slag is allowed to solidify in the outlet.

In one embodiment, the outlet is “plugged” with a soft refractory paste.An oxygen lance is provided in a position suitable to “burn” a hole intothe soft refractory paste allowing molten slag to pour out. The flow isstopped by placing refractory or other suitable material back into theoutlet. In one embodiment the outlet is covered by a movable watercooled plug. The plug is movable from a closed position to an openposition, thereby exposing the outlet to allow the molten slag toexhaust through the outlet. The molten material should not adhere to thesmooth surface of the plug because of the water cooling effect. In oneembodiment the outlet is plugged by a wedge-type device. The “wedge” ispushed in and out of outlet as required to control the exhaust of themolten slag.

In one embodiment, the slag output means also comprises a slag coolingsubsystem for cooling the molten slag to provide a solid slag product.In one embodiment, the molten slag is poured into a quench water bath.The water bath provides an efficient system for cooling the slag andcausing it to shatter into granules suitable for commercial uses, suchas for the manufacture of concrete making or for road building. Thewater bath may also provide a seal to the environment in the form of awater seal duct that extends from the base of the slag chamber down intothe water bath, thereby providing a barrier preventing outside gasesfrom entering the residue conditioning chamber.

In one embodiment of the slag cooling subsystem, the molten slag isdropped into a thick walled steel catch container for cooling. In oneembodiment, the molten slag is received in an environmentally sealed bedof silica sand or into moulds to provide solid slag suitable for smallscale processing or for testing certain parameters whenever such testingis performed. The small moulds can be control cooled in a preheatedoven. In one embodiment of the slag cooling subsystem, the molten slagis converted to a commercial product such as glass wool.

Where the residue conditioning system is provided to condition theresidue remaining after the gasification of a material that may containsa significant amount of metals, such as municipal solid waste, it islikely that a proportion of the metal will be passed through thegasification system and into the residue conditioning chamber. Thesemetals will not necessarily melt at the normal slag vitrificationtemperature, therefore, the slag reservoir could become clogged withmetal over time as it is of higher density than the molten slag. Inorder to remove accumulated metals, the chamber temperature may beperiodically raised to melt any metals and the molten metals may betapped off from the bottom of the reservoir through a metal tap port asrequired.

Where the residue being conditioned contains a proportion of unreactedcarbon, a product of the residue conditioning process will be a gashaving a potentially useful heating value, and may be appropriate foruses in downstream applications. This gas is referred to herein as“residue gas”. Gases that are produced in the residue conditioningchamber during conversion of the residue material to inert slag exit thechamber via a gas outlet. The residue gas may then be further treated ingas cooling and/or pollution abatement systems known in the art.

Accordingly, in one embodiment of the invention, the residue gas isdirected to a system provided for cooling and cleaning the gas, which isreferred to as a “solid residue gas conditioning system”. The solidresidue gas conditioning system is described in more detail above in the“Gas Conditioning System” section above. After the residue gas has beentreated, it is ready for use in downstream applications.

A Gas Homogenization System

The invention further comprises a gas homogenization system forhomogenizing the chemical composition of an input gas and adjustingother characteristics such as flow rate, pressure, and temperature ofthe gas, thereby creating a regulated gas to meet downstreamrequirements. This system enables a continual and steady stream of gasof defined characteristics to be delivered to downstream applications,for example, a gas turbine, engine or other suitable applications.

In particular, the gas homogenization system provides a gashomogenization chamber having dimensions that are designed toaccommodate a gas residence time sufficient to attain a homogeneous gasof a consistent output composition. Other elements of the gashomogenization system are designed and configured such that theregulated gas meets the performance requirements of a downstreamapplication. The system may also comprise a feedback control system tooptimize the energetics and output of the process.

The composition of the gas, which will enter the homogenization systemfrom the GCS, is determined by the gasification process and the GCS asdescribed above. The gas leaving the GCS, may be within a defined rangeof a target composition, however, over time the gas may fluctuate in itscharacteristics due to variability in the gasification process such asfeedstock composition and feed rate, airflow and temperaturefluctuations. Despite various controls to control the composition of thefinal conditioned gas as described above, fluctuations in both thepressure and temperature of the gas will typically occur over time. Inthe case of pressure, fluctuations may occur on a per second basis; andwith temperature, on a per minute basis. In one embodiment of theinvention, the pressure variance limit is selected to be less than about0.145 psi/second.

As noted above, the regulated gas exiting the gas homogenization systemhas substantially stabilized characteristics that meet thespecifications of a downstream application. Typically, machinemanufacturers will provide the requirements and tolerances allowed byspecific machinery; such gas parameters for a gas engine or gas turbinewould be known to a person skilled in the art. In one embodiment of theinvention, a gas engine may require a regulated gas composition LHV tohave a maximum of about 1% change in about 30 seconds. In one embodimentof the invention, gas engines can accept gas with HHV as low as about50BTU/scf, so long as it contains a minimum of about 12% Hydrogen. Inone embodiment of the invention, the regulated gas requires the WobbeIndex (defined as T(degrees R)/sq.rt (specific gravity)) to be +/−4% ofthe design value for use with turbine engines. In addition, a turbineengine may also require a minimum LHV of about 300 Btu/scf and a minimumpressure of about 475 psig. In one embodiment of the invention, theengine will require a regulated gas temperature greater than or equal tothe dew point temperature plus about 20° F. where relative humidity isat a maximum of about 80%.

A gas homogenization system configured in accordance with one embodimentof the invention for the production of a regulated gas comprises: achiller; a gas/liquid separator; a homogenization chamber, to which arelief valve and a pressure control valve are connected; a gasconditioning skid, comprising a gas/liquid separator and a heater; afilter; and a pressure regulating valve. The regulated gas maysubsequently be directed through a suitable conduit to an engine.

FIGS. 86 and 87 depict various embodiments of the gas homogenizationsystem configured for the production of a regulated gas. In FIG. 86, forexample, the gas homogenization system 1 comprises: a chiller 10; agas/liquid separator 12; a homogenization chamber 14, to which a reliefvalve 16 and a pressure control valve 18 are connected; a gasconditioning skid 20, comprising a gas/liquid separator 22 and a heater24; a filter 26; and a pressure regulating valve 28. The regulated gasmay subsequently be directed through a suitable conduit to an engine 30.

A substantially clean gas enters the homogenization system from the GCSat the chiller, where the temperature of the gas is appropriatelyadjusted. The gas is then delivered to the separator, by suitableconduit means, where the humidity of the gas is regulated. Followingthis, the gas enters the homogenization chamber, by way of gas inletconduit means. Once in the homogenization chamber, the gas is mixed orblended, resulting in a gas having a stabilized composition. The gasflow rate and pressure of the mixed or blended gas are further regulatedupon exit of the mixed or blended gas from the homogenization chamber.Suitable conduit means then carry the mixed or blended gas to the gasconditioning skid, where regulation of the temperature and humidity ofthe mixed or blended gas is undertaken. The mixed or blended gas,carried by suitable conduit means, is then filtered and regulated forpressure. The resulting regulated gas, now meeting the desiredrequirements for a downstream application, may be directed throughsuitable conduit means to the engine.

The homogenization system can be configured to direct regulated gas toone downstream application or to multiple downstream applications inparallel. FIGS. 88, 89 and 90 depict configurations of thehomogenization in various embodiments of the invention in which thehomogenization system delivers regulated gas to a plurality ofdownstream applications.

Typically, gas will be conveyed from a GCS to the homogenization chamberas it is generated. To ensure a uniform input gas flow rate, a draftinduction device may also be employed. Similarly, to ensure that factorssuch as gas composition, flow rate, temperature and pressure of theinput gas stream are compliant with the desired range of targetcharacteristics, the input gas may be monitored by a monitoring system,as would be known to the skilled technician, prior to homogenization.Given the outcome of the analysis of these factors, gas may then bedirected to the homogenization chamber.

The gas homogenization chamber receives conditioned gas from a GCS andencourages mixing or blending of the gas to attenuate fluctuations inthe chemical composition of the gas within the homogenization chamber.Fluctuations in other gas characteristics, such as pressure, temperatureand flow rate, can also be reduced during mixing of the gas.

In one embodiment of the invention, the dimensions of the chamber aredesigned according to the performance characteristics of an upstreamgasification system and the requirements of a downstream application,with the objective of substantially minimizing the size of the chamberas much as possible. The gas homogenization chamber is designed toreceive gas from a gasification process and retain the gas for a certainresidence time to allow for sufficient mixing or blending of the gas inorder to dampen disturbances and/or fluctuations and achieve a volume ofgas with a substantially consistent chemical composition.

In one embodiment of the invention, the dimensions of a homogenizationchamber can be calculated based on the total system response time whichincludes the process residence time between the converter and theanalyzer sample probe, plus the total system response time for thesample system, analysis and transmission time to a plant control system(PCS).

The residence time is the average amount of time that gas remains in thehomogenization chamber before being directed to a downstreamapplication. The residence time is substantially proportional to theresponse time of the related gasification system to dampen the effect ofthe rate of change of the fluctuations in the gasification reaction inorder to achieve gas characteristics that fall within accepted tolerancevalues. For example, the gas composition is retained in thehomogenization chamber long enough to determine whether it falls withinthe gas composition tolerance allowed for the particular downstreamapplication as well as to make any adjustments to the gasificationprocess to adjust for the deviance. In this way, the system can affectthe rate of change in gas characteristics so that upstream controls withfast process lags will be able to meet the specifications of adownstream application. In one embodiment, the residence time isdetermined by about 1% maximum change in the lower heating value (LHV)per 30 seconds and a maximum change in pressure of about 0.145psi/second.

Residence time of the gas in the homogenization chamber is determined bythe amount of variance in the gas characteristics. That is, the smallerthe variance in gas characteristics, the shorter the residence timerequired in the homogenization chamber to correct for this variance.

Depending on the different embodiments of the present invention, theresidence time can vary from less than about one minute to about 20minutes. In one embodiment, the residence time ranges from about 15 toabout 20 minutes. In one embodiment the residence time ranges from about10 to about 15 minutes. In one embodiment, the residence time rangesfrom about 5 to about 10 minutes. In one embodiment of the invention,the residence time ranges from about 3 to about 5 minutes. In oneembodiment of the invention, the residence time ranges from about 1 toabout 3 minutes. In one embodiment of the invention, the residence timeranges from amounts less than about one minute.

In one embodiment, the residence time is about 20 minutes. In oneembodiment the residence time is about 18 minutes. In one embodiment,the residence time is about 15 minutes. In one embodiment, the residencetime is about 13 minutes. In one embodiment, the residence time is about10 minutes. In one embodiment, the residence time is about 8 minutes. Inone embodiment, the residence time is about 6 minutes. In oneembodiment, the residence time is about 4 minutes. In one embodiment,the residence time is about 3 minutes. In one embodiment, the residencetime is about 2 minutes. In one embodiment, the residence time is about1 minute. In one embodiment, the residence time is less than about 1minute.

The volume capacity of the homogenization chamber is related to theresidence time required for a specific downstream application andfluctuations that are expected because of heterogeneity of thefeedstock. In one embodiment of the invention, the variable gas volumeranges from about 0-290 m³. In one embodiment, the variable gas volumeranges from about 0-1760 m³. In one embodiment, the variable gas volumeranges from about 0-2050 m³. In one embodiment, the variable gas volumeranges from about 0-30,000 m³. In one embodiment of the invention, thehomogenization chamber has a maximum capacity of about 290 m³. In oneembodiment, the homogenization chamber has a maximum capacity of about1800 m³. In one embodiment of the invention, the homogenization chamberhas a maximum capacity of about 2300 m³. In one embodiment of theinvention, the homogenization chamber has a maximum capacity of about30,000 m³.

The downstream application selected can directly impact the operatingpressure of the homogenization chamber. For example, a gas engine willrequire a gas pressure of about 1.2-3.0 psig while a gas turbine willrequire a gas pressure of about 250-600 psig. The mechanical designpressure of the homogenization chamber is correspondingly calculated toaccommodate the required operating pressure for a selected application.In one embodiment, the homogenization chamber has a mechanical designpressure suitable for maintaining the gas pressure for use in a gasengine. In one embodiment, the homogenization chamber has a mechanicaldesign pressure suitable for maintaining the gas pressure for use in agas turbine. In one embodiment the homogenization chamber has amechanical design pressure of about 5.0 psig. In one embodiment of theinvention, the homogenization chamber has a mechanical design pressureof about 10.0 psig. In one embodiment of the invention, thehomogenization chamber has a mechanical design pressure of about 25.0psig. In one embodiment of the invention, the homogenization chamber hasa mechanical design pressure in the range of about 100 to about 600psig.

One skilled in the art can also appreciate that to meet the requirementsof downstream applications, such as a gas engine, a lower pressuresystem would be more advantageous than for other applications, such as agas turbine, where a higher pressure gas stream would be moreappropriate.

The homogenization chamber has a mechanical design temperature tolerancethat will accommodate the gas being contained and the specifications ofthe downstream application. Typically, these temperatures will rangefrom about −40° C. to about 300° C. In one embodiment of the invention,the mechanical design temperature of the chamber ranges from about −37°C. to about 93° C.

A person skilled in the art will appreciate that the homogenizationchamber can be formed in a variety of shapes provided functionalrequirements of the homogenization system, discussed above, aresatisfied. One skilled in the art will also appreciate that the shapeand size of the chamber will depend on the gas throughput and residencetime required for a specific design, as discussed above. Cost andmaintenance are additional considerations in selecting a type ofhomogenization chamber.

Different types of homogenization chambers include, but are not limitedto gasometers, gas holders, variable volume and fixed volume tanks, suchas standard fuel tanks and surge tanks. Thus, in accordance with oneembodiment of the invention, the homogenization chamber is a standardfuel tank. In accordance with one embodiment of the invention, thehomogenization chamber is a fixed volume tank such as a surge tank. Inaccordance with one embodiment of the invention, the homogenizationchamber is a variable volume tank. In accordance with one embodiment ofthe invention, the homogenization chamber is a gasometer or gas holder.

FIG. 6 depict a homogenization chamber in one embodiment of theinvention which is a fixed-volume tank, a gas inlet, a gas outlet, arelief gas outlet, a drain, one or more pressure/temperature nozzles andone or more level switch nozzles. The drain of the tank is a feature ofthe conical bottom drainage system.

FIGS. 92 to 94 depict various embodiments of the homogenization chamber.In the embodiment depicted in FIG. 92, the gas inlet is connected to acompressor, which functions to compress the gas prior to storage in thepressure vessel. In the embodiment depicted in FIG. 93, the gas holdingchamber is defined by an inner membrane and an outer membrane. When gasexits the holding chamber, a blower, associated with the outer membrane,provides inflation to the region between the membranes. When gas isadded to the holding chamber, a regulator, adjusts the pressure of theinflated region. In the embodiment depicted in FIG. 94, thehomogenization chamber is an absorption type gas holder comprising aconstant volume tank. A cross sectional view of the tank, which acts toabsorb gas molecules, is also shown.

Typically the homogenization chamber will be located above ground.However, it is contemplated that for aesthetic reasons, or in thosejurisdictions which do not allow above ground containment of fuel, ahomogenization chamber may be located underground. Thus, in oneembodiment, the homogenization chamber is underground. In oneembodiment, the homogenization chamber is above ground. In oneembodiment of the invention, the homogenization chamber is positionedsuch that a portion thereof is underground.

It is further contemplated that a homogenization chamber can beconfigured as a homogenization system with more than one chamber or maybe configured as one or more single homogenization chambers fluidlyinterconnected in parallel. FIG. 95 depicts a configuration ofhomogenization chambers in one embodiment of the invention in which thechambers are interconnected in parallel.

A worker skilled in the art will readily appreciate that each of thefixed-volume, homogenization chamber could be independently selected asone of the above-mentioned embodiments, for example, a pressure vessel,a double-membrane gas holder, a multiple-absorption type gas holderetc., provided there is a single gas inlet and a single gas outlet forthe entire system. A worker skilled in the art would be able toascertain the suitability of such designs for a given purpose.

It is known that gas from a gasification system can be highly toxic andflammable, and in most cases will be contained outdoors exposed tovarious environmental conditions such as extreme temperature changes,rain, sun, snow, wind and the like. Accordingly, a homogenizationchamber will be manufactured from a suitably safe material. Non-limitingexamples of materials include plastics (PVC), steel, composite materialssuch as fiberglass reinforced plastic or steel, and steel alloys. Gashomogenization chambers comprising a combination of these materials arealso herein contemplated, as are metals comprising suitable internalcoatings. Coated metals, for example, can be useful for those chamberslocated underground due to the added environmental protection providedby such a coating. Coated metals may also be required to satisfygovernmental regulations.

One skilled in the art will appreciate that the gas characteristics ofthe input conditioned gas will be monitored during the gashomogenization process in order to determine whether the gas meets thedownstream requirements and what adjustments are required in order tosatisfy such requirements. Monitoring of the gas characteristics mayoccur within the homogenization chamber or prior to gas delivery to thehomogenization chamber. The gas monitoring equipment may take the formof sensing elements, response elements, and controllers that can monitorand/or regulate the composition, flow rate, temperature and pressure ofthe gas.

In one embodiment of the invention, a feedback loop can be implementedin which the gas produced is analyzed in real-time and the operation ofthe gasification system is adjusted accordingly in order to make thenecessary adjustments. In one embodiment, the homogenization chambercomprises one or more sensing elements for analyzing gas characteristicssuch as gas composition, temperature, flow rate and pressure, theconfiguration of each sensing element would be readily understood by aworker skilled in the art. For example, temperature can be measuredusing a thermocouple, or other temperature sensor format; pressure canbe measured using an absolute pressure sensor, a gauge pressure sensor,vacuum pressure sensor, differential pressure sensor or other pressuresensor; flow rate can be measured using a flowmeter or other flow ratesensor; gas composition can be measured using a gas composition sensorbased on acoustic properties, or other gas composition sensor as wouldbe readily understood.

In one embodiment, a particular sensing element can be configured tomeasure multiple characteristics of the gas, wherein these types ofsensors would be readily understood by a worker skilled in the art. Inone embodiment, the homogenization chamber further includes one or morecontrollers configured to generate instructions for transmission to oneor more response elements in order to regulate gas characteristics suchas gas composition, temperature, flow rate and pressure.

In one embodiment of the invention, multiple sensing elements arepositioned within the homogenization chamber in order to provide thecapability of gas characteristic sampling at different locations withinthe chamber, thereby providing a means for evaluation of homogeneity ofthe gas therein. Furthermore, one or more redundant sensing elements canbe positioned within the homogenization chamber in order to ensureaccurate operation of the one or more sensing elements, for examplefault detection. In addition, in one embodiment, two or more sensingelements are used to evaluate the same parameter and the measured valueof the parameter is defined as a correlation between the readingsdetermined by the two or more sensing elements.

Inlets comprising of one or more conduits is used to carry the gas fromthe gasification system to the homogenization chamber. As noted above,the upstream components of the system may optionally include one or morechillers, gas/liquid separators, induced draft devices, gas monitoringsystems, which may include temperature and pressure controllers, andcontrol valves.

The gas is transferred from the GCS to the homogenization chamber of theinvention by way of conduits that are designed to carry the gas atpredetermined temperatures and pressures. One skilled in the art willappreciate that these conduits can take the form of tubes, pipes, hoses,or the like.

As the gas is typically extracted from the GCS as it is generated, thegas flow is typically non-uniform. When the GCS is operating at lessthan atmospheric pressure, an induced draft device may convey the gasthrough the homogenization chamber. The induced draft device may belocated anywhere preceding the homogenization chamber. As would beunderstood in the field, suitable draft devices include, but are notlimited to blower fans and vacuum pumps, or other suitable flow inducingdevices.

As discussed above, the gas characteristics of the input gas may bemonitored within the homogenization chamber or prior to input. In oneembodiment, the monitoring system may be part of the inlet means and maycomprise automated equipment, such as one or more sensing elements,capable of providing a detailed assessment of the characteristics of thegas. For example, these characteristics can include continuous gaspressure and temperature monitoring plus continuous product gas flowrate and composition monitoring. A worker skilled in the art wouldreadily understand the sampling devices required to collect the aboveinformation regarding the gas. For example, temperature can be measuredusing a thermocouple, or other temperature sensor format; pressure canbe measured using an absolute pressure sensor, a gauge pressure sensor,vacuum pressure sensor, differential pressure sensor or other pressuresensor; flow rate can be measured using a flowmeter or other flow ratesensor; gas composition can be measured using a gas composition sensorbased on acoustic properties, or other gas composition sensor as wouldbe readily understood.

In one embodiment, a particular sensing element can be configured tomeasure multiple characteristics of the gas, wherein these types ofsensing elements would be readily understood by a worker skilled in theart.

Furthermore, in one embodiment, the monitoring system may include ameans for the analysis of gas operatively connected with a feedbacksystem as an integrated, on-line part of a process control system (PCS).The advantages provided by such an integrated on-line gas analysis arefiner tuning capabilities of process control and enhanced control andhomogenization capabilities for a variety of applications of the gas.

In some embodiments of the invention, the gas inlet may further comprisea means for controlling the flow rate of the gas into the homogenizationchamber, thus controlling the pressure of the gas in the chamber. Thispressure control subsystem may comprise conventional valves or shut offsystems known in the art. Several non-limiting examples of pressureregulating devices are shown for example. The pressure control systemresponds to signals from the monitoring system and may control the flowrate of the gas as well as direct the gas appropriately. In oneembodiment, the pressure control system includes a valve by whichcompliant and non-compliant gas can be directed to the homogenizationchamber and combustor or incinerator, respectively.

The regulated gas is transferred from the homogenization chamber to thedownstream application by way of regulated gas conduits that aredesigned to carry the gas at predetermined temperatures and pressures.One skilled in the art will appreciate that these conduits can take theform of tubes, pipes, hoses, or the like.

As already discussed, a monitoring system is used to monitor/control thegas either prior to its entry into the homogenization chamber or duringits residence in the homogenization chamber. Similarly, a monitoringsystem can be used to monitor the regulated gas before it is deliveredfor the downstream application. This can serve to confirm and controlthe characteristics

The regulated gas outlet may further comprise a means for controllingthe flow rate of the regulated gas from the homogenization chamber andto a downstream application. Working alternately to, or in conjunctionwith, the control system operative in the inlet, the pressure of thehomogenization chamber may be controlled. The pressure control in theoutlet may comprise conventional valves or shut off systems known in theart. As discussed above, the flow and pressure control system respondsto signals from the monitoring system employed to monitor thecharacteristics of the regulated gas as it exits the homogenizationchamber. For example, the control system may comprise a pressureregulator valve that may be adjusted to control gas flow rate andpressure by way of one or more response elements.

The regulated gas outlet may further comprise a means for heating theregulated gas as it exits the homogenization chamber. One skilled in theart would also appreciate when it is advantageous to incorporate agas/liquid separator into the system of the invention.

Typically downstream applications such as gas engines and gas turbinesare sensitive to trace elements that may enter the gas during any pointof the gas production process. In this regard, the system may compriseone or more filters of an appropriate pore size to screen out thesepotentially interfering contaminants, while substantially limiting theimpact that the filter has on gas flow rate. In one embodiment, a filteris associated with the common header to the engines. In one embodiment,each engine gas train has its own filter. In one embodiment, both of theabove-mentioned filtering approaches are used and may be configured as atwo stage filtering process.

The regulated gas outlet device may further comprise pressure regulatingvalve device for controlling the pressure of the regulated gas prior todelivery to the downstream application.

One skilled in the art will appreciate that a downstream applicationwill dictate the specific gas characteristics required for the regulatedgas. For example, the required gas pressure for the efficient operationof a gas engine will differ from those of a gas turbine. As discussedabove, a gas turbine will require a relatively high gas pressure. It iscontemplated, therefore, that in those embodiments requiring a high gaspressure, a means for gas pressurization can be included in thehomogenization system. Gas pressurization devices are well known in theart and may include a gas compressor of a variety of designs such asaxial-flow compressor, reciprocating compressor, rotary screwcompressor, centrifugal compressors. Other implementations include thediagonal or mixed-flow compressor, the scroll compressor, or other gaspressurization devices, as would be known to a worker skilled in theart.

The pressure control system may additionally comprise one or moreemergency exit ports with control valves. When gas flow cannot bereduced fast enough, for instance due to an up-stream operationalmalfunction, or a downstream failure of a gas engine, an emergencycontrol valve may be opened to release gas through an emergency exitport.

The emergency valve may be opened rapidly so that no significant change(about <1%) in gas pressure may occur. One skilled in the art willappreciate that the emergency exit port and corresponding valve may belocated at any point in the homogenization system of the invention. Inone embodiment, the emergency port is located in the homogenizationchamber. In one embodiment, the emergency port is located in the inletmeans. In one embodiment, the emergency port is located in the outletmeans.

Control System

The present invention provides a control system for the conversion ofcarbonaceous feedstock into a gas. In particular, the control system isdesigned to be configurable for use in controlling one or more processesimplemented in, and/or by, a gasification system, or one or morecomponents thereof, for the conversion of such feedstock into a gas,which may be used for one or more downstream applications. Gasificationprocesses controllable by different embodiments of the disclosed controlsystem may include in various combinations, a converter, a residueconditioner, a recuperator and/or heat exchanger system, one or more gasconditioners, a gas homogenization system and one or more downstreamapplications. Examples of these components and subsystems will bedescribed in greater detail below, which depict exemplary embodiments ofgasification systems that may be controlled by the present controlsystem.

In general, the gasification process controlled by the present inventiongenerally takes place in a converter comprising one or more processingzones and one or more heat sources, which may include in someembodiments one or more plasma heat sources. The converter alsogenerally comprises one or more feedstock feed mechanisms and/or devicesfor inputting the feedstock, which may include a single feedstock (e.g.municipal solid waste (MSW), high carbon feedstock (HCF), coal,plastics, liquid wastes, hazardous wastes, etc.), distinct feedstocks,and/or a mixed feedstock into the converter, as well as means, foradding one or more process additives, such as steam, oxidant, and/orcarbon-rich material additives (the latter of which is optionallyprovided as a secondary feedstock). The gaseous products exit theconverter via one or more output gas outlets. As will be describedfurther below, the converter main comprise a single zone and/or chamberconverter, or a multi-zone and/or chamber converter, for instancecomprising a gassifier and reformer wherein gasification andreformulation processes are implemented respectively.

In one embodiment, the application of plasma heat (e.g. via a plasmaheat source such as a plasma torch or the like), in conjunction with theinput of additives, such as steam and/or oxygen and/or carbon-richmaterial, helps in controlling the gas characteristics, such as flow,temperature, pressure and composition. The gasification system may alsoutilize plasma heat to provide the high temperature heat required togasify the feedstock, reformulate the off-gas produced thereby, and/orto melt the by-product ash and convert it to a glass-like product withcommercial value.

The gasification process controlled by the present invention may furthercomprise means for means for managing and controlling processing of thesolid by-product of the gasification process. In particular, agasification system may include a solid residue conditioner for theconversion of the solid by-products, or residue, resulting fromfeedstock-to-energy conversion processes, into a vitrified, homogenoussubstance having low leachability. The solid by-products of thegasification process may take the form of char, ash, slag, or somecombination thereof.

The gasification process controlled by the present invention may alsocomprise means for the recovery of heat from the hot product gas. Suchheat recuperation may be implemented by various heat exchangers, such asgas-to-gas heat exchangers, whereby the hot product gas is used to heatair or other oxidant, such as oxygen or oxygen enriched air, which maythen optionally be used to provide heat to the gasification process. Therecovered heat may also be used in industrial heating applications, forexample. Optionally, one or more steam generator heat exchangers may becontrolled as part of the gasification process to generate steam whichcan, for example, be used as an additive in the gasification and/orreformulation reaction(s), or to drive a steam turbine to generateelectricity, for example.

The gasification process controlled by the present invention may furtherinclude a converter gas conditioner, or other such gas conditioningmeans, to condition the product gas produced by the gasification processfor downstream use. For instance, the product gas may be directed to aconverter gas conditioner, as can gas generated from processing of theresidue in the residue converter discussed above, where it is subjectedto a particular sequence of processing steps to produce an output gassuitable for downstream use.

The gasification process controlled by the present invention may furthercomprise a gas homogenization system for providing at least a firstlevel homogenization of the product gas. For instance, by subjecting theproduct gas to a given residence time within the homogenization system,various characteristics of the gas may be at least partially homogenizedto reduce fluctuations of such characteristics. For example, thechemical composition of the product gas, as well as othercharacteristics such as flow, pressure, and/or temperature may be atleast partially stabilized by the homogenization system to meetdownstream requirements. In one embodiment, the homogenization system ofa gasification system provides a gas homogenization chamber or the likehaving dimensions that are designed to accommodate a gas residence timesufficient to attain a gas of a sufficiently consistent outputcomposition, pressure, temperature and/or flow. In general,characteristics of the homogenization system will be designed inaccordance requirements of the downstream application(s), and, withrespect to a capacity of the control system to attenuate fluctuations inproduct gas characteristics when the control system is designed withsuch intentions.

The control system operatively controls various local, regional and/orglobal processes related to the overall gasification process, andthereby adjusts various control parameters thereof adapted to affectthese processes for a selected result. Various sensing elements andresponse elements are therefore distributed throughout the controlledsystem, or in relation to one or more components thereof, and used toacquire various process, reactant and/or product characteristics,compare these characteristics to suitable ranges of such characteristicsconducive to achieving the desired result, and respond by implementingchanges in one or more of the ongoing processes via one or morecontrollable process devices.

In one embodiment, the control system is used for controlling agasification process for converting a carbonaceous feedstock into a gassuitable for use in a selected downstream application. In one example,the gasification process is controlled such that the product gas thereofmay be used in a continuous manner and/or in real-time for immediateuse. Accordingly, the control system may comprise, for example, one ormore sensors for sensing one or more characteristics of the gas to beused in the downstream application. One or more computing platforms arecommunicatively linked to these sensing elements for accessing acharacteristic value representative of the sensed characteristic(s), andconfigured to compare the characteristic value(s) with a predeterminedrange of such values defined to characterise the gas as suitable for theselected downstream application and compute one or more process controlparameters conducive to maintaining the characteristic value with thispredetermined range. A plurality of response elements may thus beoperatively linked to one or more process devices operable to affect theprocess and thereby adjust the sensed characteristic of the gas, andcommunicatively linked to the computing platform(s) for accessing thecomputed process control parameter(s) and operating the processdevice(s) in accordance therewith.

For example, the control system may be configured to control theconversion of a carbonaceous feedstock into a gas having one or morecharacteristics appropriate for downstream application(s), wherein theproduct gas is intended for use in the generation of electricity throughcombustion in a gas turbine or use in a fuel cell application. In suchapplications, it is desirable to obtain products which can be mosteffectively used as fuel in the respective energy generators.Alternatively, if the product gas is for use as a feedstock in furtherchemical processes, the composition will be that most useful for aparticular synthetic application.

In one embodiment, the control system provides a feedback, feedforwardand/or predictive control of process energetics to substantiallymaintain a reaction set point, thereby allowing the gasificationprocesses to be carried out under optimum reaction conditions to producea gas having a specified composition. For instance, the overallenergetics of the conversion of feedstock to gas can be determined andachieved using an appropriately configured gasification system, whereinvarious process characteristics may be evaluated and controllablyadjusted to influence the determination of the net overall energetics.Such characteristics may include, but are not limited to, the heatingvalue and/or composition of the feedstock, the characteristics of theproduct gas (e.g. heating value, temperature, pressure, flow,composition, carbon content, etc.), the degree of variation allowed forsuch characteristics, and the cost of the inputs versus the value of theoutputs. Continuous and/or real-time adjustments to various controlparameters, which may include, but are not limited to, heat sourcepower, additive feed rate(s) (e.g. oxygen, steam, etc.), feedstock feedrate(s) (e.g. one or more distinct and/or mixed feeds), gas and/orsystem pressure/flow regulators (e.g. blowers, relief and/or controlvalves, flares, etc.), and the like, can be executed in a manner wherebythe net overall energetics are assessed and optimized according todesign specifications.

Alternatively, or in addition thereto, the control system may beconfigured to monitor operation of the various components of agasification system for assuring proper operation, and optionally, forensuring that the process(es) implemented thereby are within regulatorystandards, when such standards apply.

In accordance with one embodiment, the control system may further beused in monitoring and controlling the total energetic impact of agasification system. For instance, a gasification system for theconversion of a feedstock may be operated such that an energetic impactthereof is reduced, or again minimized, for example, by optimising oneor more of the processes implemented thereby, or again by increasing therecuperation of waste heat generated by these processes. Alternatively,or in addition thereto, the control system may be configured to adjust acomposition and/or other characteristics (e.g. temperature, pressure,flow, etc.) of a product gas generated via the controlled process(es)such that such characteristics are not only suitable for downstream use,but also substantially optimised for efficient and/or optimal use. Forexample, in an embodiment where the product gas is used for driving agas engine of a given type for the production of electricity, thecharacteristics of the product gas may be adjusted such that thesecharacteristics are best matched to optimal input characteristics forsuch engines.

In one embodiment, the control system may be configured to adjust agasification process such that limitations or performance guidelineswith regards to reactant and/or product residence times in variouscomponents, or with respect to various processes of the overallgasification process are met and/or optimised for. For instance, in anembodiment where municipal waste is used a feedstock, it may beconsidered important to adjust the gasification process of such waste toaccount for a maximum residence time of the waste in a pre-processingand/or storage phase. For example, the waste and/or other feedstock maybe transported to the controlled system facility periodically or on anon-going basis, wherein processing of such feedstock must be controlledso to avoid and overstocking thereof (e.g. increased pre-processingresidence time) while allowing for continuous operation (e.g. reduced oravoided down-times). In such an example, a processing rate of a givenfeedstock may be controlled so to substantially match a delivery rate ofsuch feedstock, thereby allowing for a substantially constant residencetime of the delivered feedstock in a storage or pre-processing stage(e.g. a number of hours, days, weeks, etc.).

Similarly, the residence time of the feedstock within the converter of agasification system may be controlled to allow for sufficientprocessing, without depleting resources and thereby unduly reducingand/or limiting downstream processes and/or applications. For example, agiven converter configuration may allow for a relatively stableresidence time for which suitable processing of the feedstock isachieved (e.g. minutes, hours, etc.). Downstream components of theconverter may equally be controlled such that a residence timeappropriate therefor is also substantially respected. For example,streaming gas through a heat-exchange system, conditioning system and/orhomogenisation system may be best processed by such components for agiven gas flow and/or residence time. Similarly, variations in the gasflow and/or residence time may be addressed and compensated for bycontrolling various elements of such system components.

The person of skill in the art will understand that the gasificationsystem and control system, in their various embodiments, may be used ina number of processing systems having numerous independent and/orcombined downstream applications. The control system is further capable,in various embodiments, of simultaneously controlling various aspects ofa process in a continuous and/or real time manner.

Referring to FIGS. 98 and 99 the control system may comprise any type ofcontrol system architecture suitable for the application at hand. Forexample, the control system may comprise a substantially centralizedcontrol system (e.g. see FIG. 98), a distributed control system (e.g.see FIG. 99), or a combination thereof. A centralized control systemwill generally comprise a central controller configured to communicatewith various local and/or remote sensing devices and response elementsconfigured to respectively sense various characteristics relevant to thecontrolled process, and respond thereto via one or more controllableprocess devices adapted to directly or indirectly affect the controlledprocess. Using a centralized architecture, most computations areimplemented centrally via a centralized processor or processors, suchthat most of the necessary hardware and/or software for implementingcontrol of the process is located in a same location.

A distributed control system will generally comprise two or moredistributed controllers which may each communicate with respectivesensing and response elements for monitoring local and/or regionalcharacteristics, and respond thereto via local and/or regional processdevices configured to affect a local process or sub-process.Communication may also take place between distributed controllers viavarious network configurations, wherein a characteristics sensed via afirst controller may be communicated to a second controller for responsethereat, wherein such distal response may have an impact on thecharacteristic sensed at the first location. For example, acharacteristic of a downstream product gas may be sensed by a downstreammonitoring device, and adjusted by adjusting a control parameterassociated with the converter that is controlled by an upstreamcontroller. In a distributed architecture, control hardware and/orsoftware is also distributed between controllers, wherein a same butmodularly configured control scheme may be implemented on eachcontroller, or various cooperative modular control schemes may beimplemented on respective controllers.

Alternatively, the control system may be subdivided into separate yetcommunicatively linked local, regional and/or global control subsystems.Such an architecture could allow a given process, or series ofinterrelated processes to take place and be controlled locally withminimal interaction with other local control subsystems. A global mastercontrol system could then communicate with each respective local controlsubsystems to direct necessary adjustments to local processes for aglobal result.

The control system of the present invention may use any of the abovearchitectures, or any other architecture commonly known in the art,which are considered to be within the general scope and nature of thepresent disclosure.

The control system comprises response elements for controlling thereaction conditions and to manage the chemistry and/or energetics of theconversion of the carbonaceous feedstock to the output gas. In addition,the control system can determine and maintain operating conditions tomaintain ideal, optimal or not, gasification reaction conditions. Thedetermination of ideal operating conditions depends on the overallenergetics of the process, including factors such as the composition ofthe carbonaceous feedstock and the specified characteristics of theproduct gases. The composition of the feedstock may range fromsubstantially homogeneous to completely inhomogeneous. When thecomposition of the feedstock varies, then certain control parameters mayrequire continuous adjustment, via response elements, to maintain theideal operating conditions.

The control system can comprise a number of response elements, each ofwhich can be designed to perform a dedicated task, for example, controlof the flow rate of one of the additives, control of the position orpower output of one of the one or more heat sources of the gasificationsystem, or control of the withdrawal of by-product. The control systemcan further comprise a processing system, as in processor(s). In oneembodiment, the processing system can comprise a number ofsub-processing systems.

The control system may be further enhanced by interactively performingvarious system and/or process calculations defined to reflect a currentimplementation of a given gasification system. Such calculations may bederived from various system and/or process models, wherein simulation ofprocess and/or system characteristics and control parameters may be usedin a predictive and/or corrective manner to control the system orsubsystem so modeled. U.S. Pat. No. 6,817,388 provides an example ofsuch a system model, which may be used in conjunction with the controlsystem to define various operational parameters, and predicted resultsbased thereon, for use as starting points in implementing the variousprocesses of system 10. In one embodiment, these and other such modelsare used occasionally or regularly to reevaluate and/or update varioussystem operating ranges and/or parameters of the system 10 on an ongoingbasis. In one embodiment, the NRC HYSYS simulation platform is used andcan consider as inputs, waste type, any combination of input chemicalcomposition, thermo-chemical characteristics, moisture content, feedrate, process additive(s), etc. The model may also provide variousoptional interactive process optimizations to consider, for example,site and feedstock type specifics, maximization of energy recovery,minimization of emissions, minimization of capital and costs, etc.Ultimately, based on the selected model options, the model may thenprovide, for example, various operational characteristics, achievablethroughputs, system design characteristics, product gas characteristics,emission levels, recoverable energy, recoverable byproducts and optimumlow cost designs. Various exemplary representations are provided in U.S.Pat. No. 6,817,388 which are readily applicable in the present context,as would be apparent to a person skilled in the art.

The processing system and any one of the sub-processing systems cancomprise exclusively hardware or any combination of hardware andsoftware. Any of the sub-processing systems can comprise any combinationof none or more proportional (P), integral (I) or differential (D)controllers, for example, a P-controller, an I-controller, aPI-controller, a PD controller, a PID controller etc. It will beapparent to a person skilled in the art that the ideal choice ofcombinations of P, I, and D controllers depends on the dynamics anddelay time of the part of the reaction process of the gasificationsystem and the range of operating conditions that the combination isintended to control, and the dynamics and delay time of the combinationcontroller.

Important aspects in the design of the combination controller can beshort transient periods and little oscillation during transient timeswhen adjusting a respective control variable or control parameter froman initial to a specified value. It will be apparent to a person skilledin the art that these combinations can be implemented in an analoghardwired form which can continuously monitor, via sensing elements, thevalue of a characteristic and compare it with a specified value toinfluence a respective control element to make an adequate adjustment,via response elements, to reduce the difference between the observed andthe specified value.

It will further be apparent to a person skilled in the art that thecombinations can be implemented in a mixed digital hardware softwareenvironment. Relevant effects of the additionally discretionarysampling, data acquisition, and digital processing are well known to aperson skilled in the art. P, I, D combination control can beimplemented in feed forward and feedback control schemes.

In corrective, or feedback, control the value of a control parameter orcontrol variable, monitored via an appropriate sensing elements, iscompared to a specified value or range. A control signal is determinedbased on the deviation between the two values and provided to a controlelement in order to reduce the deviation. For example, when the outputgas exceeds a predetermined H₂:CO ratio, a feedback control means candetermine an appropriate adjustment to one of the input variables, suchas increasing the amount of additive oxygen to return the H₂:CO ratio tothe specified value. The delay time to affect a change to a controlparameter or control variable via an appropriate response elements issometime called loop time. The loop time, for example, to adjust thepower of the plasma heat source(s), the pressure in the system, thecarbon-rich additive input rate, or the oxygen or steam flow rate, canamount to about 30 to about 60 seconds, for example.

In one embodiment, the product gas composition is the specified valueused for comparison in the feedback control scheme described above,whereby fixed values (or ranges of values) of the amount of CO and H₂ inthe product gas are specified. In another embodiment, the specifiedvalue is a fixed value (or range of values) for the product gas heatingvalue (e.g. low heating value (LHV)).

Feedback control can be used for any number of control variables andcontrol parameters which require direct monitoring or where a modelprediction is satisfactory. There are a number of control variables andcontrol parameters of the gasification system 10 that lend themselvestowards use in a feedback control scheme. Feedback schemes can beeffectively implemented in aspects of the control system for systemand/or process characteristics which can be directly or indirectlysensed, and/or derived from sensed values, and controlled via responsiveaction using adjusted control parameters for operating one or moreprocess devices adapted to affect these characteristics.

It will be appreciated that a conventional feedback or responsivecontrol system may further be adapted to comprise an adaptive and/orpredictive component, wherein response to a given condition may betailored in accordance with modeled and/or previously monitoredreactions to provide a reactive response to a sensed characteristicwhile limiting potential overshoots in compensatory action. Forinstance, acquired and/or historical data provided for a given systemconfiguration may be used cooperatively to adjust a response to a systemand/or process characteristic being sensed to be within a given rangefrom an optimal value for which previous responses have been monitoredand adjusted to provide a desired result. Such adaptive and/orpredictive control schemes are well known in the art, and as such, arenot considered to depart from the general scope and nature of thepresent disclosure.

Feed forward control processes input parameters to influence, withoutmonitoring, control variables and control parameters. The gasificationsystem can use feed forward control for a number of control parametersuch as the amount of power which is supplied to one of the one or moreplasma heat sources, for example. The power output of the arcs of theplasma heat sources can be controlled in a variety of different ways,for example, by pulse modulating the electrical current which issupplied to the torch to maintain the arc, varying the distance betweenthe electrodes, limiting the torch current, or affecting thecomposition, orientation or position of the plasma.

The rate of supply of additives that can be provided to the converter ina gaseous or liquid modification or in a pulverized form or which can besprayed or otherwise injected via nozzles, for example can be controlledwith certain control elements in a feed forward way. Effective controlof an additive's temperature or pressure, however, may requiremonitoring and closed loop feedback control.

Fuzzy logic control as well as other types of control can equally beused in feed forward and feedback control schemes. These types ofcontrol can substantially deviate from classical P, I, D combinationcontrol in the ways the plasma reformulating reaction dynamics aremodeled and simulated to predict how to change input variables or inputparameters to affect a specified outcome. Fuzzy logic control usuallyonly requires a vague or empirical description of the reaction dynamics(in general the system dynamics) or the operating conditions of thesystem. Aspects and implementation considerations of fuzzy logic andother types of control are well known to a person skilled in the art.

Modularity of the System

One embodiment of this design is a modular plant design. Modulatedplants are facilities where each function block is pre-built components.This allows for the components to be built in a factory setting and thensent out to the facility site. These components (or modules) include allthe equipment and controls to be functional and are tested beforeleaving the factory. Modules are often built with a steel frame andgenerally incorporate a variety of possible sections, such as: GasifierBlock, Gas Quality Control System, Power Block, etc. Once on-site, thesemodules would only need to be connected to other modules and the controlsystem to be ready for plant's commissioning. This design allows forshorter construction time and economic savings due to reduced on-siteconstruction costs.

There are different types of modular plants set-ups. Larger modularplants incorporate a ‘backbone’ piping design where most of the pipingis bundled together to allow for smaller footprint. Modules can also beplaced in series or parallel in an operation standpoint. Here similartasked equipment can share the load or successively provide processingto the product stream.

One possible application of modular design in this technology is itallows more options in the gasification of multiple wastes. Thistechnology can allow for multiple gasifiers to be used in a singlehigh-capacity facility. This would allow the option of having eachgasifier co-process wastes together or separately; the configuration canbe optimized depending on the wastes.

If an expansion is required due to increasing loads, a modular designallows this technology to replace or add modules to the plant toincrease its capacity, rather then building a second plant. Modules andmodular plants can be relocated to other sites where they can be quicklyintegrated into a new location.

Function Combination

It is possible to combine the functions of different gasification trains(series of equipment) so that common functions can be carried out invessels that take in gasses or solid material from more than one stream.The following diagrams demonstrate this concept as applied toMSW/Coal/Biomass Gasification.

In these embodiments there are two trains shown although this set-up ofcombined functions between trains can occur for any number of trains andfor any feedstock per train (even if one train has a combinedfeedstock). Once a stream has been combined one may still chooseparallel handling equipment downstream; the parallel streams do not needto be of the same size even if handling the same gases.

Each Function Group Represents the Following Systems

-   -   1. Primary Gasification Chamber    -   2. Slag Chamber    -   3. Refining Chamber

None Combined, FIG. 107

-   -   In this embodiment there are two separate systems that can have        the gas streams mixed for downstream system; like the        homogenization tank or engines.

GCS Combined, FIG.

-   -   In this embodiment the gases from function vessels 2 & 3 from        each train are fed together into a single GCS which has been        sized appropriately for the gas flow.

Function 2 Combined, FIG. 108

-   -   In this embodiment the trains differ only in function vessel 1,        with all other functions being handled by the same combined        train of equipment.

Function 3 Combined, FIG. 109

-   -   In this embodiment gases from function vessels 1 go to a        combined function vessel 3; which is sized appropriately.

Function 2 & 3 Combined, FIG. 110

-   -   In this embodiment gases from function vessels 1 go to a        combined 2 and material from function vessels 1 go to a combined        function vessel 3; which are sized appropriately. Gases from        combined function vessels 2 & 3 then travel to a combined GQCS.

A worker skilled in the art will readily understand that while in theabove section we have mentioned the gasification system as comprising ofthe function blocks 1, 2 & 3 and the GCS, it can be further subdividedinto other smaller function blocks. In this case, a worker skilled inthe art will readily appreciate that the trains can be combined in alarger family of schemes depending on where the combination of thetrains is effected.

Combined Control

When there are combined streams control of the gas quality can be doneby having one gasification train run on feed-back control (operation iscorrected to maintain syngas quality to downstream applications). Therest of the trains run on feed-forward control (run within specificsbounds of gas quality). Only if the first feed-back controlled traincannot correct the syngas quality when running at optimal conditions itis switched to the optimum condition in a feed-forward control andanother train (not optimal) is switched to feed-back control to improvethe gas quality.

To gain a better understanding of the invention described herein, thefollowing examples are set forth. It will be understood that theseexamples are intended to describe illustrative embodiments of theinvention and are not intended to limit the scope of the invention inany way.

EXAMPLES Example I A System for the Conversion of Municipal Solid Waste

In this example, with reference to FIGS. 1 to 46, details of oneembodiment of the invention, including various options, are provided.This example presents details for each subsystem of the invention anddemonstrates how they work together to function as an integrated systemfor the conversion of municipal solid waste (MSW) into electricity. Oneskilled in the art can appreciate, however, that each subsystem on itsown can be considered a system. The subsystems comprising thisembodiment are: a Municipal Solid Waste Handling System; a PlasticsHandling System; a Horizontally Oriented Gasifier with Lateral TransferUnits System; a Gas Reformulating System; a Heat Recycling System; a GasConditioning System; a Residue Conditioning System; a Gas HomogenizationSystem and a Control System.

FIGS. 1 & 2 show the flow diagram and representation, for thegasification process in the different regions of the gasifierrespectively. FIG. 3 show a functional block diagram overview of theentire system 120 designed primarily for the conversion of MSW tosyngas, with the associated use of reformulated, conditioned, andhomogenized syngas in gas engines 9260 for the generation ofelectricity.

Municipal Solid Waste (MSW) Handling System

The initial MSW handling system 9200 is designed to take into account:(a) storage capability for supply of four days; (b) avoidance of longholding periods and excess decomposition of MSW; (c) prevention ofdebris being blown around; (d) control of odour; (e) access and turningspace for garbage trucks to unload; (f) minimization of driving distanceand amount of turning required by the loader 9218 transporting MSW fromthe MSW stockpile 9202 to the MSW shredding system 9220; (g) avoidanceof operational interference between loader 9218 and garbage trucks; (h)possibility of additional gasification streams to allow for plantexpansion; (i) minimum intrusion by trucks into the facility, especiallyinto hazardous areas; (j) safe operation with minimum personnel; (k)indication for the loader operator of the fill levels in the conveyorinput hoppers 9221; (l) shredding the as-received waste to a particlesize suitable for processing; and (m) remote controllability of MSW flowrate into the processor and independent control of the plastics feedrate rate (described below).

The MSW handling system 9200 comprises a MSW storage building 9210, aloader 9218, a MSW shredding system 9220, a magnetic separator 9230 anda feed conveyor 9240. A separate system 9250 is also designed forstoring, shredding, stockpiling and feeding a high carbon material(non-recyclable plastics in this example), the feed-rate of which isused as an additive in the gasification process. FIG. 4 shows an overalllayout of the entire system site. All storage and handling of MSW untilit is fed into the gasification system 120 is confined in MSW storagebuilding 9210 to contain debris and odor.

A first-in-first-out (FIFO) scheduling approach is used to minimizeexcessive decomposition of the MSW. FIFO is enabled by having access fortrucks and loaders 9218 at both ends of the MSW storage building 9210.MSW is unloaded from the trucks at one end of the building while thematerial is being transferred by the loader 9218 at the other end of theMSW storage building 9210, thus also allowing the loader 9218 to operatesafely and without interference by the trucks. When the loader 9218 hasremoved the material back to the approximate mid point 9203 of the MSWstockpile 9202 i.e. the ‘old’ material has all been used, the operationsare then changed to the opposite ends of the MSW storage building 9210.

To minimize the size of MSW storage building 9210, space for maneuveringthe garbage trucks is outside the MSW storage building 9210. This alsominimizes the size of door 9212 required as it needs only to allow atruck to reverse straight in, thus providing the best control of theescape of debris and odor. Only one door 9212 needs to be open at anytime and then only when trucks are actually unloading. Receipt of MSWwill normally take place during one period per day so that a door 9212will only be open for about one hour per day.

FIG. 5 shows a layout of the MSW storage building 9210. The MSW storagebuilding 9210 has a bunker wall 9214 to separate the MSW stockpile 9202from the aisle 9216 where the loader 9218 must drive to access the inputconveyor 9222 leading to the MSW shredding system 9220. The bunker wall9214 stops short of the ends of the MSW storage building 9210 to allowthe loader 9218 to travel from the MSW stockpile 9202 to the inputconveyor 9222 without leaving the MSW storage building 9210. Thus, thedoors 9212 at one end of the MSW storage building 9210 can be keptclosed at all times while the other end is open only when trucks areunloading or when a loader (described below) for transferring materialfrom the stockpile to the shredding system needs to exit to moveplastic.

By having the MSW storage building 9210 located adjacent and parallel tothe road 9204 and allowing for truck maneuvering at both ends of the MSWstorage building 9210, as shown in FIG. 2, both space requirements andtruck movements within the facility is reduced. The space layout designallows a truck to drive into the facility, reverse into the MSW storagebuilding 9210, dump its load and drive directly back onto the road 9204.At no times do they get near any of the process equipment or personnel.The two road entrance concept also avoids the need for an additionalroadway within the facility to enable the trucks to access both ends ofthe MSW storage building 9210.

A mechanized, bucket-based loader 9218 is used to transfer material fromthe stockpile to the shredding system. A skid steer loader design isused due to its compact size, maneuverability, ease of operation etc. Astandard commercially available skid steer has adequate capacity to feedthe MSW, clean up the stockpile floor after the trucks have unloaded andalso handle the waste plastics system shredder and process feed.

The input conveyor 9222 transports the MSW from inside the MSW storagebuilding 9210 upwards and drops it into the MSW shredding system 9220.The feed hopper 9221 for this conveyor 9222 is located entirely insidethe MSW storage building 9210 to prevent debris being blown aroundoutdoors. The conveyor 9222 has a deep trough which, combined with thecapacity of the feed hopper 9221 holds sufficient material for one hourof operation. The portion of the trough outside the MSW storage building9210 is covered to control escape of debris and odor. The conveyor 9222is controlled remotely by the process controller to match processdemands. Mirrors are provided to allow the loader operator to see thelevel of MSW in the hopper 9221 from either side. Detectors provided inthe trough alert the process controller that material is absent.

The MSW shredding system 9220 consists of an input hopper 9223, ashredder 9224 and a pick conveyor and is followed by a magnetic pick-upconveyor. The shredder 9224 ensures that the as-received MSW is suitablefor processing, by breaking any bags and cutting the larger pieces ofwaste into a size able to be processed. As the received MSW may includematerials too large and hard for the shredder 9224 to handle, thuscausing the shredder to jam, the shredder 9224 is equipped toautomatically stop when a jam is sensed, automatically reverse to clearthe jam and then restart. If a jam is still detected the shredder 9224will shut-down and send a warning signal to the controller.

The shredded waste is dropped onto a belt conveyor to be transportedunder a magnetic pick-up system and then to be dropped into the feedhopper 9239 of a screw conveyor 9240 which will feed the waste into thegasifier 2200. To avoid inadvertent feeding of excessive amounts offerrous metals through the gasifier 2200, a magnetic pick-up system 9230is located above the pick conveyor, which attracts ferrous metals thatmay be present in the shredded waste. A non-magnetic belt runs acrossthe direction of the pick conveyor, between the magnet and the waste sothat ferrous metals attracted to the magnet get moved laterally awayfrom the waste stream. The ferrous metal is later removed from themagnet and dropped onto a pile for disposal.

The MSW feed system consists of a feed hopper 9239 and screw conveyor9240 to transport shredded waste from the MSW shredder system 9220 tothe gasification chamber 2202. Shredded waste is dropped from the MSWshredder system 9220 into the feed hopper 9239, which provides a bufferof material ready to feed into the processor. The hopper has high andlow level indicators which are used to control flow from the shreddingsystem into the hopper. The conveyor 9240 is under the control of theprocess controller to match waste feed rate to meet process demands. Theuse of a screw conveyor 9240 with integral feed hopper 9239 alsoprovides gas sealing for the processor. The feed hopper 9239 isconnected to the MSW shredder system with covers to control debris andodor. The screw conveyor 9240 has an additional entry to accept shreddedplastic.

Plastics Handling System

The gasification system 120 provides for the addition of plastics as aprocess additive. The plastics are handled separately from the MSW,before being fed to the gasifier 2200.

The plastics handling system 9250 is designed to provide storage foras-received bales of plastic, shred it, place it into a stockpile 9254and feed it under independent control into the processor. The plasticshandling system 9250 comprises a plastics storage building 9255 storagefacility, a shredder 9252 with input hopper 9251, a take-away conveyor9253 and a stockpile 9254, all located in a common building 9255 tocontrol debris. A feed conveyor 9240 moves the shredded plastic into theprocessor.

The plastics storage building 9255 has the capacity to store two truckloads of plastic bales. It is closed on three sides and opens on oneside, thus providing containment of the material with access forstacking and removing bales. The building also provides protection forthe shredder 9252 and debris control and protection for the shreddedmaterial.

The shredder facilitates the plastic material meeting the processrequirements. As-received plastic is loaded into the feed hopper 9251 ofthe shredder 9252 with a loader. The shredded material drops onto atake-away conveyor 9253 that transports it up and drops it into astockpile 9254.

The shredded plastic is picked up by a loader and dropped into the inputhopper of the feed conveyor. As the conveyor is outdoors, the hopperincorporates an integral roof and upwardly extended walls to minimizeescape of plastic during filling of the hopper. The conveyor trough issealed to the trough of the MSW conveyor such that the plastic isintroduced into the gasifier 2200 via the MSW conveyor to reduceopenings into the gasifier 2200. The conveyor is a screw conveyor withthe hopper sealed to it to provide gas sealing when it containsmaterial. Detectors are located in the hopper to indicate high and lowlevels and a mirror is provided for the skid steer operator to monitorfill level. Motion of this conveyor is under the control of the processcontroller.

Converter

The converter 1200 comprises a gasifier 2200 and a Gas ReformulatingSystem (GRS) 3200. The MSW and plastics are fed into the gasifier 2200and the resulting gas is sent to the GRS 3200 where it is reformulated.Any resulting residue from the gasifier 2200 is sent to the residueconditioning system 4200.

The gasifier 2200 is designed to take into account the requirements to:(a) provide a sealed, insulated space for primary processing of thewaste; (b) introduce hot air and steam in a controlled and distributedmanner throughout the gasifier 2200; (c) enable control of the heightand movement of the waste pile through the gasifier 2200; (d) provideinstrumentation for controlling the gasification process; (e) transferthe gas to the GRS 3200; (f) remove residue for further processing; and(g) provide access to the interior for inspection and maintenance.

Referring to FIGS. 6 to 9, the gasifier 2200 comprises a horizontallyoriented refractory-lined gasification chamber 2202 having a feedstockinput 2204, inputs for hot air used for heating the gasificationchamber, input for steam which serves as a process additive, acentrally-located gas outlet 2206 to which the GRS is directly coupled,a residue outlet 2208 and various service 2220 and access 2222 ports.The gasification chamber 2202 is built as a steel weldment having astepped floor with a plurality of floor steps 2212, 2214, 2216. A systemcomprising carrier rams 2228, 2230, 2232 is used to facilitate thelateral movement of the material through the gasifier 2200. Provision isalso made for installation of instrumentation, such as thermocouples,material height detectors, pressure sensors and viewports.

The refractory lining of the gasification chamber 2202 protects it fromhigh temperatures, corrosive gases and also minimizes the unnecessaryloss of heat from the process. Referring to FIG. 10, the refractory is amultilayer design with a high density chromia layer 2402 on the inside,a middle high density alumina layer 2404 and an outer very low densityinsulboard material 2406. The refractory lines the metal shell 2408 ofthe gasification chamber. The gasification chamber 2402 is further linedwith a membrane to further protect it from the corrosive gases.

Each step 2212, 2214, 2216 of the stepped floor of gasification chamber2402 has a perforated floor 2270 through which heated air is introduced.The air hole size is selected such that it creates a restriction andthus a pressure drop across each hole sufficient to prevent wastematerials from entering the holes. The holes are tapered outwardstowards the upper face to preclude particles becoming stuck in a hole.

Referring to FIGS. 1 & 2, the conditions at the three individual stepsare designed for different degrees of drying, volatilization and carbonconversion. The feedstock is introduced into the gasification chamber2202, onto the first stage via the feedstock input 2204. The targetedtemperature range for this stage (as measured at the bottom of thematerial pile) lies between 300 and 900° C. Stage II is designed to havea bottom temperature range between 400 and 950° C. Stage III is designedto have a temperature range between 600 and 1000° C.

The three steps 2212, 2214 & 2216 of the stepped-floor, that separatethe gasification chamber 2202 into three stages of processing have theirown independently controllable air feed mechanism. The independence isachieved by using separate airboxes 2272, 2274, and 2276 which form theperforated floor 2270 at each stage. The system of carrier rams 2228,2230 & 2232 used for movement of material in the gasification chamber2202 prevents access from below steps 1 & 2, 2212 & 2214. Thus for thesestages, the airboxes 2272 & 2274 are inserted from the side. The thirdstage airbox 2276 is however inserted from below, as shown in FIGS. 7 &8.

The perforated top plate 2302 of the airboxes 2272, 2274, 2276, in thisdesign and referring to FIGS. 11 & 12, is a relatively thin sheet, withstiffening ribs or structural support members 2304 to prevent bending orbuckling. To minimize stress on the flat front and bottom sheets of theboxes, perforated webs are attached between both sheets. To allow forthermal expansion in the boxes they are attached only at one edge andare free to expand at the other three edges.

As shown in FIG. 11, the fixed edge of the Step 1 & 2 airboxes 2272 and2274 is also the connection point of the input air piping 2278. Thus,the connection flange 2280 will be at high temperature and must besealed to the cool wall of the gasifier 2200. A shroud is used, as shownin FIG. 11, to achieve this without creating stress and without using acomplex expansion joint. The hot air box 2272 and pipe 2278 are attachedto one end of the shroud 2282 and the other end of the shroud 2282 isconnected to the cool gasifier 2200. As a temperature gradient willoccur across the length of the shroud 2282, there is little or no stressat either connection. The other advantage of this arrangement is that itpositions the airbox rigidly in the required position without causingstress. The space between the shroud 2282 and the internal duct of theair box 2272 is filled with insulation to retain heat and to ensure thetemperature gradient occurs across the shroud. When the airbox is in itsoperating location in the gasification chamber 2202, the top plateopposite to the air connection is extended beyond the airbox to rest ona shelf of refractory. This provides support to the airbox duringoperation and also acts as a seal to prevent material from falling belowthe airbox. It also allows free movement to allow for expansion of theairbox, as shown in FIG. 13.

The downstream edge of the airbox is also dealt with in the same way.The upstream edge of the airbox is sealed with a resilient sheet sealing2306 between the carrier ram and the top plate of the airbox 2302.

The airbox is connected to the hot air supply piping using a horizontalflange. Therefore, only the flange has to be disconnected to remove anairbox.

The third stage airbox 2276 is inserted from below and also uses theshroud concept for sealing and locating the box to the gasifier 2200.

Sealing against dust falling around the edges of the third stage airbox2276 is achieved by having it set underneath a refractory ledge at theedge of the second stage 2214. The sides can be sealed by flexible sealsprotruding from below recesses in the sides of the refractory. Theseseals sit on the top face of the box, sealing between the walls and thebox. The downstream edge of the air box is dust sealed to the side of anextractor trough using a flexible seal. The box is reinforced withstiffeners and perforated webs between the flat faces of the air boxesto permit the use of thin sheet metal for the boxes.

The hot air pipe connection is vertical to permit removal of the thirdstage airbox 2276 after disconnecting the pipe connection.

Referring to FIG. 16, a series of a system of carrier rams 2228, 2230,2232 is used to ensure that the MSW is moved laterally along thegasifier 2200 for appropriate processing in each of the three steps2212, 2214 & 2216, and that the spent residue is moved to the residueoutlet 2208. Each of the three stage floors is serviced by its owncarrier ram. The carrier rams control both the height of the pile ateach stage as well as the total residence time in the gasificationchamber. Each carrier ram is capable of movement over the full orpartial length of that step, at variable speeds. Thus, the stage canalso be completely cleared if required.

Each carrier ram comprises an externally mounted guide portion, acarrier ram having optional guide portion engagement members, externallymounted drive system and an externally mounted control system. Thecarrier ram design comprises multiple fingers that allow the air-boxair-hole pattern to be arranged such that operation of the carrier ramsdoes not interfere with the air passing through the air-holes.

In the multiple finger carrier ram design, the carrier ram is astructure in which fingers are attached to the body of the carrier ram,with individual fingers being of different widths depending on location.The gap between the fingers in the multiple finger carrier ram design isselected to avoid particles of reactant material from bridging. Theindividual fingers are about 2 to about 3 inches wide, about 0.5 toabout 1 inch thick with a gap between about 0.5 to about 2 inches wide.

The air box airhole pattern is arranged such that operation of thecarrier rams does not interfere with the air passing through theairholes. For example, the pattern of the airholes can be such that whenheated they are between the fingers (in the gaps) and are in arrowpattern with an offset to each other. Alternatively, the airhole patterncan also be hybrid where some holes are not covered and others arecovered, such that even distribution of air is maximized (ie. areas offloor with no air input at all are minimized). In choosing the patternof the airholes, factors to consider include avoiding high velocitywhich would fluidize the bed, avoiding holes too close to gasifier wallsand ends so that channeling of air along refractory wall is avoided, andensuring spacing between holes was no more than approximately thenominal feed particle size (2″) to ensure acceptable kinetics.

A multi-finger carrier ram can have independent flexibility built-in sothat the tip of each finger can more closely comply with any undulationsin the air-box top face. This compliance has been provided by attachingthe fingers to the carrier ram main carriage using shoulder bolts, whichdo not tighten on the finger. This concept also permits easy replacementof a finger.

The end of the carrier ram finger is bent down to ensure that the tipcontacts the top of the air in the event that the relative locations ofthe carrier ram and airbox changes (for example, due to expansions).This features also lessens any detrimental effect on the process due toair holes being covered by the carrier ram, the air will continue toflow through the gap between the carrier ram and the airbox.

Referring to FIG. 13, the guide portion comprises a pair of generallyhorizontal, generally parallel elongated tracks 2240 mounted on a frame.Each of the tracks has a substantially L-shaped cross-section. Themoving element comprises a carrier ram body 2326 and one or moreelongated, substantially rectangular carrier ram fingers 2328 sized toslide through corresponding sealable opening in the gasification chamberwall.

The carrier ram fingers are constructed of material suitable for use athigh temperature. Such materials are well-known to those skilled in theart and can include stainless steel, mild steel, or mild steel partiallyprotected or fully protected with refractory. Optionally, specificindividual carrier ram fingers or all carrier ram fingers can bepartially or fully covered with refractory. Optionally, cooling can beprovided within the carrier ram fingers by fluid (air or water)circulated inside the carrier ram fingers from outside the gasificationchamber 2202.

The carrier ram fingers are adapted to sealingly engage the gasificationchamber wall to avoid uncontrolled air from entering the gasifier 2200,which would interfere with the process or could create an explosiveatmosphere. It is also necessary to avoid escape of hazardous toxic andflammable gas from the gasification chamber 2202, and excessive escapeof debris. Gas escape to atmosphere is prevented by containing thecarrier ram mechanisms in a sealed box. This box has a nitrogen purgefacility to prevent formation of an explosive gas mixture within thebox. Debris sealing and limited gas sealing is provided for each fingerof the carrier ram, using a flexible strip 2308 pressing against eachsurface of each finger of the carrier rams, as shown in FIG. 14.Alternatively, the seal can be a packing gland seal providing gas anddebris sealing for each finger.

The design of this sealing provides a good gas and debris seal for eachcarrier ram finger while tolerating vertical and lateral movements ofthe carrier ram. The seals at the sides of the fingers were the greatestchallenge as they must be compliant to the vertical and lateral motionsof the carrier ram while remaining in close contact with the carrier ramand the seals of the upper and lower surfaces of the carrier ram.Leakage of debris can be monitored by means of windows in the sealed boxand a dust removal facility is provided if the debris build-up becomesexcessive. This removal can be accomplished without breaking the sealintegrity of the carrier ram box, as shown in FIG. 15.

Referring to FIG. 15, the dust removal facility 2310 comprises a metaltray 2312 having a dust outlet 2314 equipped with a shutter 2316 andattachment site 2318 for a dust can 2332, and a manual-operated, chain2320 driven dust pusher 2322. Dust is pushed to the dust outlet 2314 bythe pusher 2322 when the operator handle 2324 is used.

Referring to FIG. 16, power for moving the carrier rams 2228, 2230 &2232 is provided by electric motors which drive the carrier ram via agearbox and roller chain system. Briefly, the power to propel thecarrier rams along the tracks is supplied by an externally mountedelectric variable speed motor 2256 which drives a motor output shaft2258 selectably in the forward or reverse direction allowing forextension and retraction of the carrier ram at a controlled rate.Position sensor 2269 transmit the carrier ram position information tothe control system. Optionally, the motor may further comprise a gearbox. Two driver sprocket gears 2260 are mounted on the motor outputshaft. The driver sprockets 2260 and corresponding driven sprockets 2262mounted on an axle 2264 operatively mesh with chain members 2266 whichare secured by brackets 2268 to the elongated rectangular block 2244.

The motors are controlled by the overall system control means which cancommand start and stop position, speed of movement and frequency ofmovement. Each carrier ram can be controlled independently. Roller chainis used for this implementation as it provides high strength andtolerates a severe duty environment. The use of two chains per carrierram provides a means of keeping the carrier rams angularly alignedwithout the need for precision guides. There is a tendency for thematerial on top of the carrier ram to be pulled back when the carrierram is withdrawn. This can be dealt with by sequencing the carrier ramswhere the lowest carrier ram 2232 is extended first; the middle carrierram 2230 is then extended which pushes material down onto the lowestcarrier ram 2232 filling the void created by that carrier rams movement;the lowest carrier ram 2232 is then retracted; the upper carrier ram2228 is then extended filling the void at the back of the middle carrierram 2230; the middle carrier ram 2230 is then retracted; new materialdropping from the feed port fills any void on the top carrier ram 2228and the top carrier ram 2228 is retracted. All these motions arecontrolled automatically and independently by the system control meansin response to system instrumentation data.

Referring to FIGS. 16 & 17, a staggered carrier ram sequence controlstrategy was implemented to facilitate movement of the carrier rams, assummarized below:

-   -   carrier ram C 2232 move fixed distance (with adjustable        setpoint), creating a pocket at the start of step C 2216.    -   carrier ram B 2230 follows as soon as carrier ram C 2232 passes        a trigger distance (trigger distance has adjustable setpoint)        carrier ram B pushes/carries material to immediately fill the        pocket at the start of step C 2230. Feedback control is to        stroke as far as necessary to block level switch C 2217, or        minimum setpoint distance if already blocked, or maximum        setpoint distance if blocking does not occur. At the same time        as carrier ram B 2230 is filling the pocket at the start of Step        C 2216, it is creating a pocket at the start of Step B 2230.    -   carrier ram A 2228 follows as soon as carrier ram B 2228 passes        a trigger distance. carrier ram A 2228 pushes/carries material        to immediately fill the pocket at the start of Step B 2214.        Feedback control is to stroke as far necessary to block level        switch B 2215, or minimum setpoint distance if already blocked,        or maximum setpoint distance if blocking does not occur. At the        same time as carrier ram A 2228 is filling the pocket at the        start of Step B 2214, it is also creating a pocket at the start        of Step A 2212. This typically triggers the feeder to run and        fill the gasifier 2200 until level switch A 2213 is blocked        again.    -   All carrier rams reverse to home position simultaneously.

Access is provided to the gasifier 2200 using a manhole at one end.During operation, this is closed using a sealable refractory linedcover. Further access is also possible by removing the third stageair-box 2276.

The residue (e.g. char or ash) remaining after gasification must beremoved from the gasifier 2200 and passed to the residue conditioningsystem (RCS) 4220. As the material is processed and moved in thegasifier 2200, the heat generated within the pile can cause melting,which will result in agglomeration of the residue. Agglomerated residuehas been shown to cause jamming in drop port type exits. In order toensure that any agglomerations do not create jamming at the exit fromthe gasification chamber 2202, a screw conveyor 2209 is used to extractthe residue from the gasification chamber 2202. The carrier ram motionpushes the residue into the extractor screw 2209 which pushes theresidue out of the gasification chamber 2202 and feed it into a residueconveyor system. Rotation of the extractor screw 2209 breaks upagglomerations before the residue is fed into the conveyor system. Thisbreaking up action is enhanced by having serrations on the edge of theextractor screw flights.

For implementing process control, various parameters have to bemonitored within the gasification chamber 2202. For example, thetemperature needs to be monitored at different points along each stageand at various heights at each stage. This is achieved usingthermocouples, which tend to need replacement during operation. In orderto accomplish this without shutting down the process, each thermocoupleis inserted into the gasification chamber 2202 via a sealed end tubewhich is then sealed to the vessel shell. This design allows the use offlexible wire thermocouples which are procured to be longer than thesealing tube so that the junction (the temperature sensing point) of thethermocouple is pressed against the end of the sealed tube to assureaccurate and quick response to temperature change. The sealed tube issealed to the gasification chamber 2202 and mechanically held in placeby means of a compression gland, which can also accommodate protrusionadjustment into the gasification chamber 2202. For temperaturemeasurements within the MSW pile, the sealed tube can result in the pilebeing held back when its movement is needed. To avoid this problem theend of the sealed tube is fitted with a deflector which prevents the MSWpile from getting blocked by the thermocouple tube.

Referring to FIGS. 18 & 19, the off-gas produced in the gasifier 2200then moves into the Gas Reformulating System (GRS) 3200. The GRS 3200 isdesigned to satisfy a wide range of requirements: (a) provide necessaryvolume for the required gas reformulation residence time; (b) provideinsulation for heat conservation and protection of the outer steelvessel; (c) provide inlets for addition of air and steam; (d) enablemixing of the gases; (e) process the gases at high temperature usingplasma torches 3208; (f) provide instrumentation for monitoring the gascomposition for process control and for enhanced performance of theplasma torch 3208; and (g) output the processed gas to a downstream heatexchanger 5200.

The gas reformulating system (GRS) 3200 provides a sealed environmentwith mounting and connection features for process air, steam, plasmatorches 3208 and torch handling mechanisms, instrumentation and exhaustof the output syngas. As shown in FIG. 20, the GRS 3200 comprises asubstantially vertically mounted refractory-lined cylindrical orpipe-like reformulating chamber 3202 having a single conically shapedoff-gas inlet 3204 to which the gasifier 2200 is connected to via amounting flange 3214. The GRS 3200 has a length-to-diameter ratio ofabout 3:1. The residence time within the GRS 3200 is 1.2 seconds. TheGRS 3200 further comprises three levels of tangentially positioned airnozzles, two tangentially located plasma torches 3208, six thermocoupleports, two burner ports, two pressure transmitter ports and severalspare ports. The high temperatures created in the GRS 3200 by the plasmatorches 3208 ensure that the molecules within the off-gas disassociateinto their constituent elements, and then combines together to formsyngas. The hot crude syngas exits the GRS 3200 via the syngas outlet3206.

Referring to FIG. 21, and as mentioned earlier, the GRS 3200incorporates supports for refractory lining. The major support featurefor the refractory is a series of shelves 3222 around the interior ofthe GRS 3200. During operation, these shelves 3222 will be atconsiderably higher temperature than the shell of the reformulatingchamber 3202. Therefore, it is necessary to avoid any waste of heat byconduction to the GRS 3200, while providing allowance for differentialexpansion. Also, the shelves 3222 must be capable of supporting theconsiderable weight of the refractory. These requirements were met bymaking the shelves 3222 segmented with expansion gaps between segmentsto allow for the expansion. Also, there is a gap between the shelf 3222and the wall to avoid heat transfer. To take the weight of therefractory, each shelf segment is supported by a number of gussets 3224welded to the wall, as shown in FIG. 21. Expansion of the shelf 3222along its length would create stress and possibly failure in the gussets3224 if they were welded to the gussets 3224. However, by resting theshelf 3222 on the gussets 3224 without welding, the shelf 3222 isallowed to expand freely. To hold the segment into its correct location,it is welded to the center gussets 3224 only where the expansion issmall and even then only the outer portion is welded. This minimizes anystress on the gussets 3224 and potential buckling of the shelf 3222.

The top of the reformulating chamber 3202 is capped with arefractory-lined lid 3203 thereby creating a sealed enclosure. The wholeGRS 3200 is coated with a high temperature resistant membrane internallyto prevent corrosion by the unrefined off-gas. It is painted on theexterior surfaces with a thermo-chromic paint to reveal hot spots due torefractory failure or other causes.

The refractory used is a multilayer design with a high density layer onthe inside to resist the high temperature, erosion and corrosion that ispresent in the GRS 3200. Outside the high density material is a lowerdensity material with lower resistance properties but higher insulationfactor. Outside this layer, a very low density foam board material withvery high insulation factor is used because it will not be exposed toabrasion of erosion. The outside layer, between the foam board and thevessel steel shell is a ceramic blanket material to provide a compliantlayer to allow for differential expansion between the solid refractoryand the vessel shell. Vertical expansion of the refractory is providedfor by means of a compressible refractory layer separating sections ofthe non-compressible refractory. The compressible layer is protectedfrom erosion by overlapping but extendible high density refractory.

As shown in FIGS. 22, 23 & 25, air is injected into the off-gas streamby three levels of air nozzles that include four jets at the lowerlevel, and another six jets at upper level, in which three jets areslightly higher than other three to create cross-jet mixing effects toachieve better mixing. Angular blowing of the air into the GRS 3200,achieved using deflector at the tip of the input nozzle, also results inbetter mixing while allowing the inlet pipes and flanges to be squarewith the reformulating chamber 3202. The improved mixing of the gases inthe GRS 3200 improves the reformulation of the syngas. This is achievedby inducing a swirling action at the base of the reformulating chamber3202 by making use of the process air velocity. Air is injected into theoff-gas stream through swirl ports 3212 to create a swirling motion orturbulence in the off-gas stream thereby mixing the off-gas and creatinga re-circulating vortex pattern within the GRS 3200.

As mentioned earlier, the GRS 3200 also includes two tangentiallymounted 300 kW, water cooled, copper electrode, NTAT, DC plasma torches3208 mounted on a sliding mechanism, as shown in FIG. 24. The DC plasmatorches 3208 are powered from a DC power supply. Thermocouples arepositioned at various locations within the GRS 3200 to ensure that thetemperature of the syngas is maintained at about 1000° C.

The plasma torches 3208 require periodic maintenance and it is mostdesirable that they are replaceable with the process still running. Asmentioned earlier, this implementation uses two torches 3208 in the GRS3200 when strictly only one is needed for operation. Removal andreplacement of the plasma torches 3208 have to be done in the presenceof high temperature toxic and flammable gas in the GRS 3200. Inaddition, the torch 3208 will also need to be removed in the event offailure of the torch cooling system to protect it from the heat in theGRS 3200.

These challenges are met by mounting the torch 3208 on a slidingmechanism that can move the torch 3208 into and out of the reformulatingchamber 3202. The torch 3208 is sealed to the reformulating chamber 3202by means of a sealing gland. This gland is sealed against a gate valve3209, which is, in turn, mounted on and sealed to the vessel. To removea torch 3208, it is pulled out of the reformulating chamber 3202 by theslide mechanism. Initial movement of the slide disables the high voltagetorch power supply for safety purposes. The gate valve 3209 shutsautomatically when the torch 3208 has retracted past the gate valve 3209and the coolant circulation is stopped. The hoses and cable aredisconnected from the torch 3208, the gland is released from the gatevalve 3209 and the torch 3208 is lifted away by a hoist.

Replacement of a torch 3208 is done using the reverse of the aboveprocedure; the slide mechanism can be adjusted to permit variation ofthe insertion depth of the torch 3208.

For the sake of simplicity and safety, all the above operations exceptfor the closing of the gate valve 3209 are carried out manually. Thegate valve 3209 is operated mechanically so that operation is automatic.A pneumatic actuator 3210 is used to automatically withdraw the torch inthe event of cooling system failure. Compressed air for operating thepneumatic actuator 3210 is supplied from a dedicated air reservoir sothat power is always available even in the event of electrical powerfailure. The same air reservoir provides the air for the gate valve3209. An electrically interlocked cover is used a further safety featureby preventing access to the high voltage torch connections.

Residue Conditioning System

The residue remaining after the gasification must be rendered inert andusable before disposal. Referring to FIG. 26, this is done by extractingit from the gasifier 2200 into a plasma-based residue conditioningchamber (RCC) 4220, melting it and rendering it into an inert moltenslag 4202, cooling and shattering the molten slag 4202 into granulesusing a quench tank 4240 before transfer to a slag stockpile 4204 readyfor removal from the site. The final by-product is suitable for use asroad fill or concrete manufacture.

As mentioned earlier, the movement of residue from the gasifier 2200 iscomplicated by the potential for agglomeration caused due to the heatgenerated within the pile. This problem is solved by using a screw typeconveyor 2209 at the outlet end of the gasifier 2200. The conveyor hasserrated edges on the screw flights to break up any agglomeratedmaterial.

Referring to FIG. 27, the residue is then taken to the RCC 4220 by meansof a main conveyor 4210 system comprising a series of screw conveyors.This conveyor system 4210 also takes the residue from the GCS baghousefilter 6230 downstream and passes it onto the RCC 4220. To minimize thenumber of entry ports to the RCC 4220, the residue from all sources iscombined before introduction to the RCC 4220. This avoids enlarging theRCC 4220 to cater to multiple feed sources. In order for gasification tocontinue during RCC 4220 downtime the residue may be diverted. In whichcase it must be re-introduced into the RCC feed system. The overallschematic of the residue conditioning system is shown in FIG. 26.

As shown in FIG. 28, the residue is dropped into the RCC 4220, where itaccumulates in a reservoir 4222 whose depth is determined by the heightof a weir 4224, and undergoes heating by a plasma torch 4230. As thelevel of the molten slag rises within the reservoir 4222 it runs overthe weir 4224, dropping into a quench tank 4240. The water tank 4240ensures that the RCC 4220 is sealed to the atmosphere. Any metals whichhave not been removed during the MSW handling system stage istransferred to the RCC 4220 and will not necessarily be melted at theslag's normal vitrification temperature. Thus, the reservoir 4222 couldbecome clogged with metal as it is of higher density than the moltenslag. To avoid this, the reservoir temperature is periodically raised tomelt any metals and the molten metals are tapped off from the bottom ofthe crucible.

Due to the very high temperatures needed to melt the residue andparticularly the constituent metals in it, the refractory is subjectedto very severe operational demands. These include corrosion and erosion,particularly at the slag waterline, in addition to the high temperature.Also the refractory must provide good insulation to conserve heat andthe RCC 4220 must be as small as possible. The refractory is selected toprovide an inner lining of very high resistance to heat, corrosion anderosion. The layers of refractory outside the lining are then selectedto greater insulation.

It is anticipated that the crucible refractory in particular willrequire periodic maintenance. To allow for this, the bottom of the RCC4229 with the crucible can be removed without disturbing any connectionsto the top of the RCC 4221. This is accomplished by suspending the RCCfrom its support structure 4270 rather than setting it onto a structure,as shown in FIGS. 29 & 31. Thus the bottom of the RCC 4229 with thereservoir can be dropped away from the top of the RCC 4221 withouthaving to disconnect any connections. Also the entire RCC can be removedby disconnecting the connections and lowering it. This avoids the needto lift the conveyor 4260 and piping out of the way.

When the molten slag drops into the quench tank 4240 it is cooled andshattered into granular form. A slag conveyor 4260 then removes thegranular slag 4203 from the quench 4240 and places it into a stockpile4204 for disposal or further use, as shown in FIG. 30. The slag dropport is sealed to the environment by means of a water trap consisting ofa shroud sealed to the RCC 4220 at the top and with its lower edgesubmerged in the quench medium. The same quench medium seals the slagconveyor 4260 from the RCC 4220.

The gases produced in the RCC 4220 are treated similarly to the gasesproduced in the converter 1200. Referring to FIGS. 28, 32 & 32A, theresidue gas exits the RCC 4220 via the gas outlet 4228 and is directedto a residue gas conditioner (RGCS) 4250. It undergoes a pre-coolingstep in an indirect air-to-gas heat exchanger 4252 prior to being passedthrough a baghouse filter 4254 that removes particulates and heavy metalcontaminants. The residue gas is then cooled using a second heatexchanger 4256 before it is passed through an activated carbon bed 4258for the further removal of heavy metals and particulate matter.Referring to FIG. 3, the cleaned and conditioned residue gas is divertedback to the downstream GCS 6200 to feed back with the syngas stream fromthe converter 1200.

Referring to FIGS. 33 & 35, the raw syngas exits the converter 1200 andpasses through a Heat Recycling System. In this embodiment, the heatrecycling system is implemented using a syngas-to-air Heat Exchanger(HX) 5200 where the heat is transferred from the syngas stream to astream of air. Thus, the syngas is cooled while the resulting hot streamof air is fed back to the converter 1200 as process air. The cooledsyngas then flows into a Gas Conditioning System (GCS) 6200, where thesyngas is further cooled and cleaned of particulates, metals and acidgases sequentially. The cleaned and conditioned syngas (with desiredhumidity) is sent to the SRS 7200 before being fed to gas engines 9260where electricity is generated. The functions of the major components(equipment) in the system after the converter 1200 and RCS 4200 areoutlined in Table 1, in the sequence in which the syngas is processed.These major components are shown in FIG. 34.

TABLE 1 Steps after Converter 1200 and RCS 4200 Subsystem or equipmentMain Function Heat Exchanger 5200 Cool down syngas and recover sensibleheat Evaporative Cooler 6210 Further cooling down of syngas prior tobaghouse Dry Injection System 6220 Heavy metal adsorption Baghouse 6230Particle or dust collection HCL Scrubber 6240 HCl removal and syngascooling/ conditioning Carbon Filter Bed 6260 Further mercury removal H₂SRemoval System 6270 H₂S removal and elemental sulfur recovery RGCS 4250RCC off-gas cleaning and cooling Syngas Storage 7230 Syngas storage andhomogenization Chiller 7210; Gas/Liquid Humidity control Separator 7220Gas Engines 9260 Primary driver for electricity generation Flare Stack9299 Burning syngas during start-up

Syngas-to-air Heat Exchanger

The output syngas leaving the GRS 3200 is at a temperature of about 900°C. to 1100° C. In order to recover the heat energy in the syngas, theraw syngas exiting from GRS 3200 is sent to a shell-tube typesyngas-to-air heat exchanger (HX) 5200. Air enters the HX 5200 atambient temperature, i.e., from about −30 to about 40° C. The air iscirculated using air blowers 5210, and enters the HX 5200 at a ratebetween 1000 Nm³/hr to 5150 Nm³/hr, typically at a rate of about 4300Nm³/hr.

Referring to FIG. 35, the syngas flows vertically through the tube sideand the air flows in a counter-clockwise fashion through the shell side.The syngas temperature is reduced from 1000° C. to between 500° C. and800° C., (preferably about 740° C.) while the air temperature isincreased from ambient temperature to between 500° C. and 625° C.(preferably about 600° C.). Referring to FIG. 3, the heated exchange-airis recirculated back into the converter 1200 for gasification.

The HX 5200 is designed specifically for high level of particulates inthe syngas. The flow directions of the syngas and the air are designedto minimize the areas where build up or erosion from particulate mattercould occur. Also, the gas velocities are designed to be high enough forself cleaning while still minimizing erosion.

Due to the significant temperature difference between the air andsyngas, each tube 5220 in the HX 5200 has its individual expansionbellows. This is essential to avoid tube rupture, which can be extremelyhazardous since the air will enter the syngas mixture. Possibility fortube rupture is high when a single tube becomes plugged and therefore nolonger expands/contracts with the rest of the tube bundle.

Multiple temperature transmitters are placed on the gas outlet box ofthe gas-to-air heat-exchanger 5200. These are used to detect anypossible temperature raise that occurs due to combustion in the event ofan air leak into the syngas. The air blower 5210 is automatically shutdown in such a case.

The material for the gas tubes in the HX 5210 has to be carefullyselected to ensure that corrosion is not an issue, due to concerns aboutsulphur content in the syngas and its reaction at high temperatures. Inour implementation, Alloy 625 was selected.

Gas Conditioning System (GCS)

In general, a gas conditioning system (GCS) 6200 refers to a series ofsteps which converts the crude syngas obtained after the heat exchanger5200 into a form suitable for downstream end applications. In ourimplementation, the GCS 6200 can be broken down into two main stages.Stage 1 comprises of: (a) an evaporative cooler (dry quench) 6210; (b) adry injection system 6220; and (c) a baghouse filter (used forparticular matter/heavy metal removal) 6230. Stage 2 comprises of (d) aHCl scrubber 6240; (e) a syngas (process gas) blower 6250; (f) a carbonfilter bed (mercury polisher) 6260; (g) a H₂S (sulphur) removal system6270; and (h) humidity control using a chiller 7210 and gas/liquidseparator 7220.

The heat exchanger 5200 before the GCS 6200 is sometimes considered aspart of Stage 1 of the GCS 6200. The syngas (process gas) blower 6250typically includes a gas cooler 6252 which is sometimes mentionedseparately in Stage 2 of the GCS 6200. Also, humidity control mentionedhere as part of Stage 2 of the GCS 6200 is often considered part of theSRS 7200 further downstream to the GCS 6200.

FIG. 33 shows a block diagram of the GCS 6200 implemented in our system.This is also an example of a converging process in which the GCS 6200 isintegrated with the RGCS 4250. FIG. 34 shows a view of the layout of theGCS.

After initial cooling in the heat exchanger 5200, the input syngas isfurther cooled by dry quenching 6210, which lowers the syngastemperature and also prevents condensation. This is achieved using anevaporative cooling tower (a.k.a ‘dry quench’) 6210 by direct injectionof water into the gas stream in a controlled manner (adiabaticsaturation). The water is atomized before it is sprayed co-currentlyinto the syngas stream. As no liquid is present in the cooling, theprocess is also called dry quench. When the water is evaporated, itabsorbs the sensible heat from syngas thus reducing its temperature from740° C. to between 150° C. and 300° C. (typically about 250° C.).Controls are added to ensure that water is not present in the exitinggas. The relative humidity at the exiting gas temperature is thereforestill below 100%.

Referring to FIGS. 36 & 37, once the gas stream exits the evaporativecooling tower 6210, activated carbon, stored in a hopper, ispneumatically injected into the gas stream. Activated carbon has a veryhigh porosity, a characteristic that is conducive to the surfaceadsorption of large molecular species such as mercury and dioxin.Therefore, most of the heavy metals (cadmium, lead, mercury etc.) andother contaminants in the gas stream are adsorbed on the activatedcarbon surface. The spent carbon granules are collected by the baghouse6230 and recycled back to the RCS 4200 for further energy recovery asdescribed in the next step. For obtaining efficient adsorption, it isnecessary to ensure that the syngas has sufficient residence time inthis stage. Other materials such as feldspar, lime, and other absorbentscan also be used instead of, or in addition to, activated carbon in thisdry injection stage 6220 to capture heavy metals and tars in the syngasstream without blocking it.

Referring to FIG. 37, particulate matter and activated carbon with heavymetal on its surface is then removed from the syngas stream in thebaghouse 6230, with extremely high efficiency. The operating parametersare adjusted to avoid any water vapour condensation. All particulatematter removed from the syngas stream forms a filter cake which furtherenhances the efficiency of the baghouse 6230. So while new non-coatedbags have a removal efficiency of 99.5%, the baghouse 6230 is typicallydesigned for 99.9% particulate matter removal efficiency. The baghouse6230 employs lined fiber glass bags, unlined fibre glass bags or P84basalt bags and is operated at a temperature between 200° C. and 260° C.

When the pressure drop across the baghouse 6230 increases to a certainset limit, nitrogen pulse-jets are used to clean the bags. Nitrogen ispreferred to air for safety reasons. The residue falling from theoutside surface of the bags are collected in the bottom hopper and aresent to the residue conditioner 4200 for further conversion or disposal.Special reagents can be used to absorb the high molecular weighthydrocarbon compounds (tars) in order to protect the baghouse 6230. FIG.37 shows the schematic of the baghouse respectively. The baghouse usescylindrical filters which do not require support.

A typical operational specification of the baghouse 6230 (assuming theinput is fly-ash with heavy metals) is as follows:

Design Gas flow rate 9500 Nm3/hr Dust loading 7.4 g/Nm3 Cadmium 2.9mg/Nm3 Lead 106.0 mg/Nm3 Mercury 1.3 mg/Nm3 Guaranteed filtration systemoutlet: Particulate matter 11 mg/Nm3 (about 99.9% removal) Cadmium 15μg/Nm3 (about 99.65% removal) Lead 159 μg/Nm3 (about 99.9% removal)Mercury 190 μg/Nm3 (about 90% removal)

The quantity of residue contaminated with heavy metals exiting thebaghouse 6230 is large. Therefore, as shown in FIGS. 27 & 33, thisresidue is sent to the plasma-based RCC 4220 for conversion intovitreous slag 4203. Referring to FIGS. 32 & 33, the secondary gas streamcreated in the RCC 4220 is then treated in a separate residue gasconditioner (RGCS) 4250 with the following Stage 1 processes: cooling inan indirect air-to-gas heat exchanger 4252 and removal of particulatematter and heavy metals in a smaller baghouse 4254. The smaller baghouse4254 is dedicated to treating the secondary gas stream generated in theRCC 4220. As shown in FIG. 33, additional steps carried out by the RGCS4250 include cooling the gas further using a gas cooler 4256, andremoving heavy metals and particulate matter in a carbon bed 4258.Referring to FIG. 3, the processed secondary syngas stream is thendiverted back to the GCS 6200 to feed back into the primary input syngasstream prior to the baghouse filter 6230.

The quantity of residue removed from the bag-house 4254 of the RGCS 4250is significantly less compared to the baghouse 6230 in the GCS 6200. Thesmall baghouse 4254 acts as a purge for the heavy metals. The amount ofheavy metals purged out of the RGCS 4250 will vary depending on MSW feedcomposition. A periodic purge is required to move this material tohazardous waste disposal, when the heavy metals build-up to a specifiedlimit.

Below is a typical design specification for the smaller RGCS baghouse4254, once again assuming that the input is fly-ash with heavy metals:

Design Gas flow rate 150 Nm3/hr Dust loading 50 g/Nm3 Cadmium 440 mg/Nm3Lead 16.6 mg/Nm3 Mercury 175 mg/Nm3 Guaranteed filtration system outlet:Particulate matter 10 mg/Nm3 (about 99.99% removal) Cadmium 13 μg/Nm3(about 99.997% removal) Lead 166 μg/Nm3 (about 99.999% removal) Mercury175 μg/Nm3 (about 99.9% removal)

The GCS 6200 may comprise direct and indirect feedback or monitoringsystems. In our implementation, both the GCS and RGCS baghouse filtershave a dust sensor on the exit (direct monitoring) to notify of a bagrupture. If a bag rupture occurs, the system is shutdown formaintenance. Optionally, the water stream in the HCl scrubber 6240 canbe analyzed at start-up to confirm particulate matter removalefficiency.

Referring to FIG. 38, the particulate-free syngas stream exiting fromthe baghouse 6230 is scrubbed in a packed tower using a re-circulatingalkaline solution to remove any HCl present. This HCl scrubber 6240 alsoprovides enough contact area to cool down the gas to about 35° C. Acarbon bed filter 6260 is used to separate the liquid solution frompotential soluble water contaminants, such as metals, HCN, ammonia etc.The HCl scrubber 6240 is designed to keep the output HCl concentrationat about 5 ppm. A waste water bleed stream is sent to a waste waterstorage tank 6244 for disposal, as shown in FIG. 39.

For metallurgical considerations, the HCl scrubber 6240 is locatedupstream of the gas blower 6250. An exemplary schematic diagram of anHCl scrubber 6240 including associated components such as heatexchangers 6242 is shown in FIG. 38. FIG. 39 shows an exemplary systemfor collecting and storing waste water from the GCS 6200. A carbon bedis added to the water blowdown to remove tars and heavy metals from thewastewater. Typical specification for the HCl scrubber 6240 is asfollows:

Design Gas flow rate 9500 Nm3/hr Normal Inlet/Max HCl loading toscrubber 0.16%/0.29% HCl outlet concentration   5 ppm

After HCl removal, a gas blower 6250 is employed which provides thedriving force for the gas through the entire system 120 from theconverter 1200 to the gas engines 9260 downstream. The blower 6250 islocated upstream of the mercury polisher 6260 as the latter has a bettermercury removal efficiency under pressure. This also reduces the size ofthe mercury polisher 6260. FIG. 3 show schematic of the entiregasification system 120 including the position of the process gas blower6250.

The blower 6250 is designed using all upstream vessel design pressuredrops. It is also designed to provide the required pressure fordownstream equipment pressure losses to have a final pressure of ˜2.1 to3.0 psig (typically 2.5 psig) in the HC 7230. As the gas is pressurizedwhen passing through the blower 6250, its temperature rises to about 77°C. A built-in gas cooler 6252 is used to reduce the temperature back to35° C., as maximum operating temperature of the H₂S removal system 6270is about 40° C.

A carbon bed filter 6260 is used as a final polishing device for anyheavy metal remaining in the syngas stream. Its efficiency is improvedwhen the system is under pressure instead of vacuum, is at lowertemperature, gas is saturated, and when the HCl is removed so that isdoes not deteriorate the carbon. This process is also capable ofabsorbing other organic contaminants, such as dioxins from the syngasstream if present. The carbon bed filter 6260 is designed for over 99%mercury removal efficiency.

The performance of this system is measured by periodically analyzing thegas for mercury. Corrections are made by modifying the carbon feed rateand monitoring the pressure drop across the polisher 6260, and byanalyzing the carbon bed efficiency via sampling.

Typical specification for the carbon bed filter 6260 is as follows:

Design Gas flow rate 9500 Nm3/hr Normal/Max Mercury loading 190μg/Nm3/1.3 mg/Nm3 Carbon bed life 3-5 years Guaranteed mercury carbonbed outlet 19 μg/Nm3 (99%)

The H₂S removal system 6270 was based on SO₂ emission limitationoutlined in A7 guide lines of the Ministry of Environment, Ontario,Canada, which states that syngas being combusted in the gas engines willproduce SO₂ emission below 15 ppm. The H₂S removal system 6270 wasdesigned for an output H₂S concentration of about 20 ppm. FIG. 40 showsthe details of the H₂S removal system 6270.

The Shell Paques Biological technology was selected for H₂S removal6270. This technique consists of two steps: First, syngas from thecarbon bed filter 6260 passes through a scrubber 6272 where H₂S isremoved from syngas by re-circulating an alkaline solution. Next, thesulphur containing solution is sent to a bioreactor 6274 forregeneration of alkalinity, oxidation of sulfide into elemental sulphur,filtration of sulphur, sterilization of sulphur and bleed stream to meetregulatory requirements. The H₂S removal system 6270 is designed for 20ppm H₂S outlet concentration.

Thiobacillus bacteria are used in the bioreactor 6274 to convertssulfides into elemental sulphur by oxidation with air. A control systemcontrols the air flow rate into the bio-reactor to maintain sulphurinventory in the system. A slip stream of the bio reactor 6274 isfiltered using a filter press 6276. Filtrate from filter-press 6276 issent back to the process, a small stream from this filtrate is sent as aliquid bleed stream. There are two sources of discharge; one soliddischarge—sulphur with some biomass and one liquid discharge—water withsulphate, carbonate and some biomass. Both streams are sterilized beforefinal disposal.

Typical specification for the H₂S removal system 6270 is as follows:

Design Gas flow rate 8500 Nm3/hr Normal/Max H₂S loading 353 ppm/666 ppmGuaranteed H₂S outlet for system ppm

After the H₂S removal, a chiller 7210 is used to condense the water outof the syngas and reheat it to a temperature suitable for use in the gasengines 9260. The chiller 7210 sub-cools the gas from 35° C. to 26° C.The water condensed out from the input gas stream is removed by agas/liquid separator 7220. This ensures that the gas has a relativehumidity of 80% once reheated to 40° C. (engine requirement) after thegas storage prior to being sent to the gas engines 9260.

The following table gives the major specifications of the entire GCS6200:

Quench Tower 6210 quench gas from 740□C. to 200□C. in 2 sec residencetime Dry Injection 6220 90% mercury removal efficiency Baghouse Filter6230 99.9% Particulate removal efficiency 99.65% Cadmium removalefficiency 99.9% Lead removal efficiency HCl Scrubber 6240 99.8% HClremoval efficiency Gas Blower 6250 Zero leak seal rotary blower GasCooler 6252 0.5 MBtu/hr cooling load Carbon Bed Filter 6260 99% mercuryremoval efficiency H₂S Scrubber 6270 H₂S at scrubber outlet - 20 ppmBioreactor 6274 Maximum regeneration efficiency with minimum blow-downFilter Press 6276 2 days sulphur removal capacity Homogenization Chamber2 min gas storage capacity 7230

As noted above, the GCS 6200 converts an input gas to an output gas ofdesired characteristics. FIG. 33 depicts an overview process flowdiagram of this GCS system 6200 which is integrated with a gasificationsystem 120 and downstream application. Here, the secondary gas streamgenerated in the RCS 4200 is fed into the GCS 6200.

The Residue Gas Conditioner (RGCS)

As mentioned earlier, the residue from the GCS baghouse 6230 which maycontain activated carbon and metals is purged periodically by nitrogenand conveyed to the RCC 4220, where it is vitrified. The gas coming outof the RCC 4220 is directed through a residue gas conditioner (RGCS)4250 baghouse 4254 to remove particulates and is cooled by a heatexchanger 4256 before entering an activated carbon bed 4258. Thebaghouse 4254 is also periodically purged based on pressure drop acrossthe system. The residue collected in the RGCS baghouse 4254 is disposedby appropriate means. The combustible gas exiting from the RGCS 4250 asa secondary gas stream is sent back to the main GCS system 6200 to fullyutilize the recovered energy.

SynGas Regulation System

The cleaned and cooled syngas from the GCS 6200 enters a gas regulationsystem. In this example, the gas regulation system is a syngasregulation system (SRS) 7200 designed to ensure that the syngas flowingto the downstream gas engines 9260 is of consistent gas quality. The SRS7200 serves to smooth out short-term variations in gas composition(primarily its low heating value—LHV) and its pressure. While thedownstream gas engines 9260 will continue to run and produce electricityeven with short-term variations in the LHV or pressure of the syngas, itmay deviate from its threshold emission limits due to poor combustion orpoor fuel to air ratio.

Referring to FIG. 41, the SRS 7200 comprises a chiller 7210, agas/liquid separator 7220 and a homogenization chamber (HC) 7230. Thegas is heated on the exit of the gas storage prior to the gas engines9260 to meet engine temperature requirements.

Two types of homogenization chambers (HC) are available: a fixed volumeHC and a variable volume HC. The latter is typically more useful toreduce flow and pressure fluctuation while the former is more useful toreduce LHV fluctuations. LHV fluctuations are more prominent in ourapplication due to the nature of the MSW feedstock. A fixed volume HC isalso typically more reliable than variable volume in terms of itsconstruction and maintenance.

FIG. 42 show the schematic of the homogenization chamber (HC) 7230 usedin this implementation. It is designed to hold about 2 minutes of syngasflow. This hold up time meets the gas engine guaranteed norms on LHVfluctuation specifications of about 1% LHV fluctuation/30 sec. Theresidence time up to the gas analyzer 8130 is typically about 30 sec(including analysis and feedback). The maximum LHV fluctuation istypically about 10%. Thus, to average this out and get 3% LHVfluctuation, >1.5 min storage is needed. The 2 min storage allows forsome margin.

The HC 7230 is operated at a range of 2.2 to 3.0 psig to meet the fuelspecifications of the downstream gas engines 9260. The exiting gaspressure is kept constant using a pressure control valve. The HC 7230 isdesigned for a maximum pressure of 5 psig and a relief valve isinstalled to handle unusual overpressure scenarios.

The 2 min hold up time of the HC 7230 also provides enough storage toreduce pressure fluctuations. For our design, the allowable pressurefluctuation for the gas engine 9260 is 0.145 PSI/sec. In the case of adownstream failure of the gas engine 9260, a buffer may be required(depending on control system response time and 30-35 sec gas residenttimes) to provide time to slow down the process or to flare the excessgas.

Typical syngas flow rate into the HC 7230 is at ˜8400 Nm3/hr. Therefore,for a hold up time of 2 min, the HC's volume has to be about 280 m3.

The HC 7230 is free-standing and is located outside where it will beexposed to snow, rain and wind. Therefore, the dimensions of the HC 7230are designed to meet mechanical engineering requirements. Its supportstructure interfaces with a concrete foundation.

As some water will condense out of the syngas, a bottom drain nozzle isincluded in the design of the HC 7230. To assist in the drainage of theHC 7230, its bottom is intentionally designed to not be flat, but as aconical bottom with a skirt. Traced/insulated drain piping is used toform the drain flange. As the water within the HC 7230 has to gravitydrain to the floor drain, the HC 7230 is kept slightly elevated.

The HC 7230 is designed to meet the following design requirements.

Normal/Maximum Inlet Temperature 35° C./40° C. Normal/Maximum OperatingPressure 1.2 psig/3.0 psig Normal/Maximum Gas Inlet Flow Rate 7000Nm³/hr/8400 Nm³/hr Normal/Maximum Gas Outlet Flow Rate 7000 Nm³/hr/8400Nm³/hr Relative Humidity 60%-100% Storage Volume 290 m³ MechanicalDesign Temperature −40° C. to 50° C. Mechanical Design Pressure 5.0 psig

The material used for the HC 7230 has to take into account both themechanical design requirements above and the typical gas compositiongiven below. Corrosion is particularly a concern due to the presence ofwater, HCl, and H₂S.

N₂ 47.09% CO₂  7.44% H₂S 20 ppm H₂O  3.43% CO 18.88% H₂ 21.13% CH₄ 0.03% HCl  5 ppm

The following openings are provided in the HC 7230:

-   -   One 36″ manhole near the bottom for accessibility;    -   One 6″ flange at the top for relief;    -   One 16″ flange on the shell for gas inlet;    -   One 16″ flange on the shell for gas outlet;    -   Six 1″ flanges on the shell (2 for pressure, 1 for temperature        and 3 as spares);    -   One 2″ flange at the bottom of HC (drain); and    -   One 1″ flange on the bottom cone for level switches.

In addition to satisfying the design requirements, the HC 7230 alsoprovides:

-   -   Openings, manhole covers, and blind flanges for all spare        nozzles.    -   A ladder allowing safe access, (e.g. with railing) to the roof        and relief valve.    -   Required lifting hooks and anchor bolts.    -   A concrete ring wall.    -   Interior and exterior coatings of the HC 7230, if required.    -   Insulation and heat tracing of the bottom of the HC 7230.    -   A concrete slab for support.

The gas engine 9260 design requires that the inlet gas be of a specificcomposition range at a specified relative humidity. Therefore, thecleaned gas that exits the H₂S scrubber 6270 is sub-cooled from 35° C.to 26° C. using a chiller 7210. Any water that is formed due to thecondensation of the gas stream is removed by the gas/liquid separator7220. This ensures that the syngas has a relative humidity of 80% oncereheated to 40° C., a typical requirement for gas engines 9260.

A gas blower 6250 is used to withdraw syngas from the system byproviding adequate suction through all the equipment and piping as perspecifications below. The blower design took heed to good engineeringpractice and all applicable provincial and national codes, standards andOSHA guidelines. Operation of the blower 6250 was at about 600 Volts, 3phase, and 60 Hz.

The gas blower 6250 was designed to meet following functionalrequirements.

Normal gas inlet temperature 35 C. Normal gas suction pressure −1.0 psigNormal gas flow rate 7200 Nm3/hr Maximum gas flow rate 9300 Nm3/hrMaximum gas suction temperature 40 C. Normal discharge pressure 3.0 psigNormal discharge temperature (after gas cooler) <35 C. Mechanical designpressure 5.0 psig Relative Humidity of gas at blower inlet 100% GasMolecular Weight 23.3 Cooling water supply temperature (product gascooler) 29.5 C. Maximum acceptable gas discharge temperature 40 C.(after product gas cooler) Turn down ratio  10%

The typical gas composition (wet basis) drawn is as follows:

CH₄ 0.03% CO 18.4% CO₂ 7.38% H₂ 20.59%  Normal/Max H₂S 354/666 ppm H₂O5.74% Normal/Max HCl 5 ppm/100 ppm N₂ 47.85% 

As the syngas is flammable and creates an explosive mixture with air,the blower 6250 is configured such that there is minimal to no airintake from the atmosphere, and minimal to no gas leak to theatmosphere. All service fluids, i.e., seal purges are done with nitrogenand a leak-free shaft seal is used. Advanced leak detection systems areemployed to monitor leaks in either direction.

In addition to the design criteria above, the blower 6250 also provides:

-   -   An explosion proof motor with leak-free blower shaft seal.    -   A gas cooler 6252.    -   A silencer with acoustic box to meet noise regulation of 80 dBA        at 1 m.    -   A common base plate for the blower and motor.    -   An auxiliary oil pump with motor, and all required        instrumentations for blower auxiliary system.    -   All instruments and controls (i.e. low and high oil pressure        switch, high discharge pressure and temperature switch,        differential temperature and pressure switch). All switches are        CSA approved discharge pressure gauge, discharge temperature        gauge, oil pressure and temperature gauge. All instruments are        wired at a common explosion proof junction box and the VFD is        controlled by a pressure transmitter installed upstream of the        blower.    -   A zero leaks discharge check valve.    -   Equipment safety system to prevent blower from excessive        pressure/vacuum/shut off discharge (e.g. systems like PRV and        recycle line).

As the gas blower 6250 is located outside the building, exposed to rain,snow and wind. The gas blower 6250 is configured to withstand thefollowing environmental conditions.

Elevation above mean sea level 80 m Latitude 45° 24′ N Longitude 75° 40′W Average atmospheric pressure 14.5 psia Maximum summer dry bulbtemperature 38° C. Design summer dry bulb temperature 35° C. Designsummer wet bulb temperature 29.4° C. Minimum winter dry bulb temperature36.11° C. Mean wind velocity 12.8 ft/sec Maximum wind velocity 123ft/sec Design wind velocity 100 mph/160 kph Prevailing wind directionMainly from south and west Seismic Information Zone 3

Since the blower 6250 works in an environment where explosive gases maybe present, all instruments and electrical devices installed on syngaspipes or within about 2 meter distance are designed for theclassification of Class 1, zone 2.

For ensuring reliability, proper access for inspection and maintenanceis provided, as is access to isolate and correct faults quickly. Whilethe blower 6250 can be operated continuously (24/7), frequent start/stopoperation is more common during process stabilization are contemplated.

The material of construction was chosen based on design conditions andgas composition. For example, electrical circuit boards, connectors andexternal components were coated or otherwise protected to minimizepotential problems from dirt, moisture and chemicals. Control panels andswitches are of robust construction, designed to be operated bypersonnel with work gloves.

Generally, variable speed drive (VSD) with a flow range of 10% to 100%is employed for motor control. Over-voltage and overload protection areincluded. The motor status, on/off operation and change of speed aremonitored and controlled remotely through the distributed control system(DCS).

Once the regulated gas exits the HC 7230, it is heated to the enginerequirement and directed to the gas engines 9260.

Gas Engines

Five reciprocating GE Jenbacher gas engines 9260 with 1MW capacity eachare used to produce electricity. So, the full capacity of electricitygeneration is 5 MW. Optionally, any of the gas engines 9260 can beturned off depending on the overall requirements. The gas engine 9260 iscapable of combusting low or medium heating value syngas with highefficiency and low emissions. However, due to the relatively low gasheating value (as compared to fuels such as natural gas) the gas engines9260 have been de-rated to operate around 700 kW at their most efficientoperating point. Optionally, the downstream application can be expandedto include another gas engines 9260 to make a total of six.

Flare Stack

An enclosed flare stack 9299 will be used to burn syngas duringstart-up, shut-down and process stabilization phases. Once the processhas been stabilized the flare stack 9299 will be used for emergencypurposes only. The flare stack 9299 is designed to achieve a destructionefficiency of about 99.99%.

Control System

In this implementation, the gasification system 120 of the presentexample comprises an integrated control system for controlling thegasification process implemented therein, which may include variousindependent and interactive local, regional and global processes. Thecontrol system may be configured to enhance, and possibly optimize thevarious processes for a desired front end and/or back end result.

A front-to-back control scheme could include facilitating the constantthroughput of feedstock, for example in a system configured for thegasification of MSW, while meeting regulatory standards for this type ofsystem. Such front-to-back control scheme could be optimized to achievea given result for which the system is specifically designed and/orimplemented, or designed as part of a subset or simplified version of agreater control system, for instance upon start-up or shut-down of theprocess or to mitigate various unusual or emergency situations.

A back-to-front control scheme could include the optimization of aproduct gas quality or characteristic for a selected downstreamapplication, namely the generation of electricity via downstream gasengines 9260. While the control system could be configured to optimizesuch back-end result, monitoring and regulation of front-endcharacteristics could be provided in order to ensure proper andcontinuous function of the system in accordance with regulatorystandards, when such standards apply.

The control system may also be configured to provide complimentaryresults which may be best defined as a combination of front-end andback-end results, or again as a result flowing from any point within thegasification system 120.

In this implementation, the control system is designed to operate as afront-to-back control system upon start-up of the gasification process,and then progress to a back-to-front control system when initialstart-up perturbations have been sufficiently attenuated. In thisparticular example, the control system is used to control thegasification system 120 in order to convert feedstock into a gassuitable for a selected downstream application, namely as a gas suitablefor consumption by a gas engine 9260 in order to generate electricity.In general, the control system generally comprises one or more sensingelements for sensing various characteristics of the gasification system120, one or more computing platforms for computing one or more processcontrol parameters conducive to maintaining a characteristic valuerepresentative of the sensed characteristic within a predetermined rangeof such values suitable for the downstream application, and one or moreresponse elements for operating process devices of the gasificationsystem 120 in accordance with these parameters.

For example, one or more sensing elements could be distributedthroughout the gasification system 120 for sensing characteristics ofthe syngas at various points in the process. One or more computingplatforms communicatively linked to these sensing elements could beconfigured to access characteristic values representative of the sensedcharacteristics, compare the characteristic values with predeterminedranges of such values defined to characterize the product gas assuitable for the selected downstream application, and compute the one ormore process control parameters conducive to maintaining thesecharacteristic values within these predetermined ranges. The pluralityof response elements, operatively linked to one or more process devicesand/or modules of the gasification system operable to affect the processand thereby adjust the one or more characteristics of the product gas,can be communicatively linked to the one or more computing platforms foraccessing the one or more computed process control parameters, andconfigured to operate the one or more processing devices in accordancetherewith.

The control system may also be configured to provide for an enhancedfront-end result, for example, for an enhanced or constant consumptionand conversion rate of the input feedstock, or again as part ofstart-up, shut-down and/or emergency procedure, or again, configured toimplement the process of the gasification system 120 so to achieve apredetermined balance between front-end benefits and back-end benefits,for instance enabling the conversion of the feedstock to produce aproduct gas suitable for a selected downstream application, whilemaximizing throughput of feedstock through the converter. Alternative orfurther system enhancements could include, but are not limited to,optimising the system energy consumption, for instance to minimise anenergetic impact of the system and thereby maximise energy productionvia the selected downstream application, or for favouring the productionof additional or alternative downstream products such as consumableproduct gas(es), chemical compounds, residues and the like.

A high-level process control schematic is provided for this example inFIG. 43, wherein the process to be controlled is provided by thegasification system 120 described above. FIG. 44 provides an alternativedepiction of the gasification system 120 and control system of FIG. 3 toidentify exemplary characteristics and sensing elements associatedtherewith. As described above, the gasification system 120 comprises aconverter 1200, comprising a gasifier 2200 and GRS 3200 in accordancewith the present example, for converting the one or more feedstocks(e.g. MSW and plastics) into a syngas and a residue product. The system120 further comprises a residue conditioning system (RCS) 4200 and aheat exchanger 5200 conducive to recuperating heat form the syngas and,in this example, using this recuperated heat for heating the air inputadditive used in the converter 1200. A gas conditioning system (GCS)6200 for conditioning (e.g. cooling, purifying and/or cleaning) thesyngas is also provided, and a SRS 7200 used for at least partiallyhomogenizing the syngas for downstream use. As depicted herein, residuemay be provided to the RCS 4200 from both the converter 1200 and the GCS6200, the combination of which being conditioned to yield a solidproduct (e.g. vitrified slag 4203) and a syngas to be conditioned andcombined with the converter syngas for further conditioning,homogenization and downstream use.

In FIGS. 43 and 44, various sensing and response elements are depictedand configured to provide various levels of control for the gasificationsystem 120. As discussed hereinabove, certain control elements may beused for local and/or regional system controls, for example in order toaffect a portion of the process and/or subsystem thereof, and therefore,may have little or no effect on the overall performance of the system.For example, while the GCS 6200 may provide for the conditioning andpreparation of the syngas for downstream use, its implementation, andvariations absorbed thereby, may have little effect on the generalperformance and output productivity of the gasification system 120.

On the other hand, certain control elements may be used for regionaland/or global system controls, for example in order to substantiallyaffect the process and/or gasification system 120 as a whole. Forexample, variation of the feedstock input via the MSW handling system9200 and/or plastics handling means 9250 may have a significantdownstream effect on the product gas, namely affecting a change incomposition and/or flow, as well as affect local processes within theconverter 1200. Similarly, variation of the additive input rate, whetheroverall or discretely for different sections of the converter 1200, mayalso have a significant downstream effect on the product gas, namely tothe gas composition and flow. Other controlled operations, such asreactant transfer sequences within the converter 1200, airflowdistribution adjustments, plasma heat source power variations and othersuch elements may also effect characteristics of the product gas and maythus be used as a control to such characteristics, or again be accountedfor by other means to reduce their impact on downstream application.

In FIGS. 43 and 44, various sensing elements are depicted and used inthe present example to control various local, regional and globalcharacteristics of the gasification process. For instance, thegasification system 120 comprises various temperature sensing elementsfor sensing a process temperature at various locations throughout theprocess. In FIG. 43, one or more temperature sensing elements areprovided for respectively detecting temperature variations within theconverter 1200, in relation to the plasma heat source 3208, and inrelation to the residue conditioning process in RCS 4200. For example,independent sensing elements (commonly identified by temperaturetransmitter and indicator control 8102 of FIG. 43) may be provided forsensing temperatures T1, T2 and T3 associated with the processes takingplace within Stages 1, 2 and 3 of the gasifier 2200 (e.g. see FIG. 44).An additional temperature sensing element 8104 may be used to sensetemperature T4 (e.g. see FIG. 44) associated with the reformulatingprocess of the GRS 3200 and particularly associated with the outputpower of the plasma heat source 3208. In this example, a temperaturesensing element 8106 is also provided for sensing a temperature withinthe RCC 4220 (e.g. temperature T5 of FIG. 44), wherein this temperatureis at least partially associated with the output power of the residueconditioner plasma heat source 4230. It will be appreciated that othertemperature sensing elements may also be used at various pointsdownstream of the converter 1200 for participating in different local,regional and/or global processes. For example, temperature sensingelements can be used in conjunction with the heat exchanger 5200 toensure adequate heat transfer and provide a sufficiently heated airadditive input to the converter 1200. Temperature monitors may also beassociated with the GCS 6200 to ensure gases conditioned thereby are nottoo hot for a given sub-process, for example. Other such examples shouldbe apparent to the person skilled in the art.

The gasification system 120 further comprises various pressure sensingelements operatively disposed throughout the gasification system 120.For instance, a pressure sensing element (depicted as pressuretransmitter and indicator control 8110 in FIG. 1) is provided forsensing a pressure within the converter 1200 (depicted in the example ofFIG. 2 as particularly associated with GRS 3200), and operativelyassociated with blower 6500 via speed indicator control, variablefrequency drive and motor assembly 8113 for maintaining an overallpressure within the converter 1200 below atmospheric pressure; in thisparticular example, the pressure within the converter 1200, in oneembodiment, is continuously monitored at a frequency of about 20 Hz andregulated accordingly. In another embodiment, the blower is maintainedat a frequency of about 20 Hz or above in accordance with operationalrequirements; when blower rates are required below 20 Hz an overridevalve may be used temporarily. A pressure sensing element 8112 is alsoprovided in operative association with the RCC 4220 and operativelylinked to a control valve leading residue conditioner gas from the RCC4220 to the GCS 6200. Pressure sensing element 8116, is also providedfor monitoring input air pressure to the heat exchanger 5200 and isoperatively linked to blower 5210 for regulating same via speedindicator control, variable frequency drive and motor assembly 8120. Apressure control valve 8115 is provided as a secondary control tooverride and adjust pressure within the system when the syngas blowerspeed 6250 falls below the blower's minimum operating frequency

Another pressure sensing element 8114 is further provided with the SRS7200 and operatively linked to control valve 7500 for controlled and/oremergency release of syngas via flare stack 9299 due to excess pressure,for example during start-up and/or emergency operations. This pressuresensing element 8114 is further operatively linked to control valve 8122via flow transmitter and control indicator 8124 to increase a processadditive input flow to the converter 1200 in the event that insufficientsyngas is being provided to the SRS 7200 to maintain continuousoperation of the gas engines 9260, for example. This is particularlyrelevant when the control system is operated in accordance with aback-to-front control scheme, as will be described in greater detailbelow. Note that in FIG. 44, the air flow sensing element 8124 andcontrol valve 8122 are used to regulate the additive air flows to Stages1, 2 and 3 of the gasifier 2200, as depicted by respective flows F1, F2and F3, and additive air flow to the GRS 3200, as depicted by flow F4,wherein relative flows are set in accordance with a pre-set ratiodefined to substantially maintain pre-set temperature ranges at each ofthe process stages. For example, a ratio F1:F2:F3:F4 of about 36:18:6:40can be used to maintain relative temperatures T1, T2 and T3 withinranges of about 300-600° C., 500-900° C. and 600-1000° C. respectively,or optionally within ranges of about 500-600° C., 700-800° C. and800-900° C., respectively, particularly upon input of additionalfeedstock to compensate for increased combustion due to increasedvolume, as described below.

The system 120 also comprises various flow sensing elements operativelydisposed throughout the system 120. For instance, as introduced above, aflow sensing element 8124 is associated with the air additive input tothe converter 1200 and operatively linked to the control valve 8122 foradjusting this flow, for example in response to a detected pressure dropwithin the SRS 7200 via sensing element 8114. A flow sensing element8126 is also provided to detect a syngas flow to the SRS 7200, valuesderived from which being used to regulate both an air additive inputrate as a fast response to a decrease in flow, and adjust a feedstockinput rate, for example in accordance with the currently defined fuel toair ratio (e.g. the (MSW+plastics):(Total additive air input) ratiocurrently in use), via MSW and/or plastics feeding mechanisms 9200 and9250 respectively, for longer term stabilisation; this again isparticularly useful when the system is operated in accordance with aback-to-front control scheme, as described below. In this example theair to fuel ratio is generally maintained between about 0 to 4 kg/kg,and during normal operation is generally at about 1.5 kg/kg. A flowsensing element 8128 may also be provided to monitor flow of excess gasto the flare stack 9299, for example during start-up, emergency and/orfront-to-back control operation, as described below.

FIGS. 43 and 44 also depict a gas analyser 8130 for analyzing acomposition of the syngas as it reaches the SRS 7200, the control systembeing configured to use this gas composition analysis to determine asyngas fuel value and carbon content and adjust the fuel to air ratioand MSW to plastics ratio respectively and thereby contribute toregulate respective input rates of MSW and plastics. Once again, thisfeature is particularly useful in the back-to-front control schemeimplementation of the control system, described in greater detail below.

Not depicted in FIGS. 43 and 44, but described above with reference toan exemplary embodiment of the gasifier 2200, is the inclusion ofvarious sensing elements configured for detecting a height of reactantwithin the gasifier 2200 at various locations, namely at steps 1, 2 and3 2212, 2214 & 2216. These sensing elements may be used to control themotion of the lateral transfer means, such as carrier rams 2228, 2230 &2232 to enhance effective processing within the gasifier 2200. In suchan example, a carrier ram sequence controller would both affectcomputation of an actual feedstock input rate, as would variation in thedesired feedstock input rate need to be communicated to the carrier ramsequence controller. Namely, the carrier ram sequence controller can beused to adjust a feedstock input rate, and the control system, incommunication with the carrier ram sequence controller, may be used tocompensate for variations induced by changes in the carrier ram sequence(e.g. to address issues raised due to various detected reactantdistributions) in downstream processes.

FIG. 45 provides a control flow diagram depicting the various sensedcharacteristic values, controllers (e.g. response elements) andoperating parameters used by the control system of the present example,and interactions there between conducive to promoting proper andefficient processing of the feedstock. In this figure:

a converter solids levels detection module 8250 is configured tocooperatively control a transfer unit controller 8252 configured tocontrol motion of the transfer unit(s) 8254 and cooperatively control atotal MSW+HCF feed rate 8256;a syngas (product gas) carbon content detection module 8258 (e.g.derived from gas analyser 8130) is operatively coupled to a MSW:HCFratio controller 8260 configured to cooperatively control an MSW/HCFsplitter 8262 for controlling respective MSW and HCF feed rates 8264 and8266 respectively;a syngas (product gas) fuel value determination module 8268 (e.g.LHV=c1*[H₂]+c2*[CO], where c1 and c2 are constants and where [H₂] and[CO] are obtained from the syngas analyser 8130) is operatively coupledto a Fuel:Air ratio controller 8270 for cooperatively controlling thetotal MSW+HCF feed rate 8256 directed to the MSW/HCF splitter 8262 andthe transfer unit controller 8252;a syngas flow detection module 8272 is operatively coupled to a totalairflow controller 8274 for controlling a total airflow 8276 andcooperatively control the total MSW+HCF feed rate 8256; anda process temperature detection module 8278 is operatively coupled to atemperature controller(s) 8280 for controlling an airflow distribution8282 (e.g. Ft, F2, F3 and F4 of FIG. 2) and plasma heat 8284 (e.g. viaPHS 1002).

In this configuration, in order to determine the amount of air additiveto input into the gasification system 120 to obtain a syngas compositionwithin an appropriate range for the downstream application, or againwithin a range conducive to increasing the energetic efficiency and/orconsumption of product gas, the control system may be configured tocompute a control parameter based on an acquired characteristic valuefor the LHV (e.g. from analysis of [H₂] and [CO] of syngas). Forinstance, by setting the temperature and pressure constant, or at adesired set point, a global system parameter may be defined empiricallysuch that the air input parameter may be estimated with sufficientaccuracy using a linear computation of the following format:

[LHV]=a[Air]

wherein a is an empirical constant for a particular system design anddesired output characteristics. Using this method, it has beendemonstrated that the gasification system 120 of the present example maybe operated efficiently and continuously to meet regulatory standardswhile optimising for process efficiency and consistency.

FIG. 46 provides an alternative control flow diagram depicting thevarious sensed characteristic values, controllers (e.g. responseelements) and operating parameters that can be used by a slightlymodified configuration of the control system and interactions therebetween conducive to promoting proper and efficient processing of thefeedstock. In this figure:

a converter solids levels detection module 8350 is configured tocooperatively control a transfer unit controller 8352 configured tocontrol motion of the transfer unit(s) 8354 and cooperatively control atotal MSW+HCF feed rate 8356;a syngas (product gas) carbon content detection module 8358 (e.g.derived from gas analyser 8130) is operatively coupled to a MSW:HCFratio controller 8360 configured to cooperatively control an MSW/HCFsplitter 8362 for controlling respective MSW and HCF feed rates 8364 and8366 respectively;a syngas (product gas) [H₂] content detection module 8367 (e.g. obtainedfrom the syngas analyser 8130) is operatively coupled to a Fuel:Airratio controller 8370 for cooperatively controlling the total MSW+HCFfeed rate 8356 for cooperatively controlling the transfer unitcontroller, the MSW/HCF splitter 8362, the steam flow calculation andthe total airflow;a syngas (product gas) [CO] content detection module 8369 (e.g. obtainedfrom the syngas analyser 8130) is operatively coupled to a Fuel:Steamratio controller 8371 for cooperatively controlling the steam flowcalculation for controlling the steam addition rate (note: steamadditive input mechanism may be operatively coupled to the converter1200 (not shown in FIGS. 1 and 2) and provided to compliment airadditive and participate in refining the chemical composition of thesyngas);a syngas flow detection module 8372 is operatively coupled to a totalairflow controller 8374 for cooperatively controlling a total airflow8376 and cooperatively controlling the total MSW+HCF feed rate 8356; anda process temperature detection module 8378 is operatively coupled to atemperature controller 8380 for controlling an airflow distribution 8382(e.g. Ft, F2, F3 and F4 of FIG. 44) and plasma heat 8384 (e.g. via PHS1002).

In this configuration, in order to determine the amount of air additiveand steam additive to input into the gasification system 120 to obtain asyngas composition within an appropriate range for the downstreamapplication, or again within a range conducive to increasing theenergetic efficiency and/or consumption of product gas, the controlsystem may be configured to compute control parameters based on acquiredcharacteristic values for [H₂] and [CO]. For instance, by setting thetemperature and pressure constant, or at a desired set point, globalsystem parameters may be defined empirically such that the air and steaminput parameters may be estimated with sufficient accuracy using alinear computation of the following format:

$\begin{bmatrix}H_{2} \\{CO}\end{bmatrix} = {\begin{bmatrix}a & b \\c & d\end{bmatrix}\begin{bmatrix}{Air} \\{Steam}\end{bmatrix}}$

wherein a, b, c and d are empirical constants for a particular systemdesign and desired output characteristics. The person of skill in theart will appreciate that although simplified to a linear system, theabove example may be extended to include additional characteristicvalues, and thereby provide for the linear computation of additionalcontrol parameters. Higher order computations may also be considered torefine computation of control parameters as needed to further restrictprocess fluctuations for more stringent downstream applications. Usingthe above, however, it has been demonstrated that the gasificationsystem 120 of the present example may be operated efficiently andcontinuously to meet regulatory standards while optimizing for processefficiency and consistency.

It will be appreciated that the various controllers of the controlsystem generally operate in parallel to adjust their respective values,which can include both absolute (e.g. total air flow) and relativevalues (e.g. feed to air ratio), although it is also possible for someor all of the controllers to operate sequentially.

As discussed above, a front-to-back (or supply-driven) control strategyis used in the present example during start-up operation of the system120 where the converter 1200 is run at a fixed feed rate of MSW. Usingthis control scheme, the gasification system 120 allows for processvariations to be absorbed by the downstream equipment such as gasengines 9260 and flare stack 9299. A small buffer of excess syngas isproduced, and a small continuous flare is hence used. Any extra syngasproduction beyond this normal amount can be sent to the flare,increasing the amount flared. Any deficiency in syngas production firsteats into the buffer, and may eventually require generator power outputto be reduced (generators can be operated from 50-100% power output viaan adjustable power set point) or further system adjustments to beimplemented by the control system, as described below. This controlscheme is particularly amenable to start-up and commissioning phases.

The main process control goals of this front-to-back control schemecomprise stabilizing the pressure in the HC 7230, stabilizing thecomposition of the syngas being generated, controlling pile height ofmaterial in the gasification chamber 2202, stabilizing temperatures inthe gasification chamber 2202, controlling temperatures in thereformulating chamber 3202, and controlling converter process pressure.

When using GE/Jenbacher gas engines 9260, the minimum pressure ofproduct gas is about 150 mbar (2.18 psig), the maximum pressure is about200 mbar (2.90 psig), the allowed fluctuation of fuel gas pressure isabout +/−10% (+/−17.5 mbar, +/−0.25 psi) while the maximum rate ofproduct gas pressure fluctuation is about 10 mbar/s (0.145 psi/s). Thegas engines 9260 have an inlet regulator that can handle smalldisturbances in supply pressure, and the holdup in the piping and HC actsomewhat to deaden these changes. The control system however still usesa fast acting control loop to act to maintain suitable pressure levels.As mentioned above, the converter 1200 in this control scheme is run atsufficient MSW feed rate to generate a small buffer of excess syngasproduction, which is flared continuously. Therefore the HC 7230 pressurecontrol becomes a simple pressure control loop where the pressurecontrol valves in the line from HC 7230 to the flare stack 9299 aremodulated as required to keep the HC pressure within a suitable range.

The control system generally acts to stabilize the composition of thesyngas being generated. The gas engines 9260 can operate over a widerange of fuel values, provided that the rate of change is not excessive.The allowable rate of change for Lower Heating Value (LHV) relevant inthis example is less than 1% fluctuation in syngas LHV per 30 second.For hydrogen based fuels, the fuel gas is adequate with as little as 15%hydrogen by itself, and the LHV can be as low as 50 btu/scf (1.86MJ/Nm3). The system volume and HC 7230 aid in stabilizing the rate ofchange of LHV by providing about 2 minutes of syngas production.

In this control scheme, the product gas composition can be measured bythe gas analyzer 8130 installed at the inlet of the HC 7230, or proximalthereto. Based on this measurement, the control system can adjust thefuel-to-air ratio (i.e. slightly increase/decrease MSW feed raterelative to air additive input air) in order to stabilize the gas fuelvalue. Increasing either the MSW or plastics feed relative to the airaddition increases the fuel value of the gas. It will be appreciated,however, that this control action may have a relatively long responsetime depending on the overall implementation of the gasification system120, and as such, may be tuned to prevent long-term drift rather thanrespond to short-term variation.

While the plastics feed is by itself a much richer fuel source (e.g. LHVof about twice that of MSW), it is typically added in a ratio of about1:20 (0 to 14%) with the MSW, and therefore, in accordance with thisexample, it is not the dominant player in terms of fuel being added tothe system. Since it can be uneconomical to add too much plastics to thegasification system 120, the plastics feed may be used as a trim ratherthan as a primary control. In general, the plastics feed is ratioed tothe total feed with the ratio optionally adjusted to stabilize the totalcarbon exiting the gasification system 120 in the syngas, as measured bythe gas analyzer 8130. This may thus have for affect to dampenfluctuations in MSW fuel value.

In addition, a reactant pile level control system may be used to aid inmaintaining a stable pile height inside the converter 1200. Stable levelcontrol may prevent fluidization of the material from process airinjection which could occur at low level and to prevent poor temperaturedistribution through the pile owing to restricted airflow that wouldoccur at high level. Maintaining a stable level may also help maintainconsistent converter residence time. A series of level switches in thegasification chamber 2202 may be used, for example, to measure piledepth. The level switches in this example could include, but are notlimited to, microwave devices with an emitter on one side of theconverter and a receiver on the other side, which detects eitherpresence or absence of material at that point inside the converter 1200.The inventory in the gasifier 2200 is generally a function of feed rateand carrier ram motion (e.g. carrier ram motion), and to a lesserdegree, the conversion efficiency.

In this example, the Stage 3 carrier ram(s) sets the converterthroughput by moving at a fixed stroke length and frequency to dischargeresidue from the gasifier 2200. The Stage 2 carrier ram(s) follows andmoves as far as necessary to push material onto Stage 3 and change theStage 3 start-of-stage level switch state to “full”. The Stage 1 carrierram(s) follows and moves as far as necessary to push material onto Stage2 and change the Stage 2 start-of-stage level switch state to “full”.All carrier rams are then withdrawn simultaneously, and a scheduleddelay is executed before the entire sequence is repeated. Additionalconfiguration may be used to limit the change in consecutive strokelengths to less than that called for by the level switches to avoidexcess carrier ram-induced disturbances. The carrier rams may be movedfairly frequently in order to prevent over-temperature conditions at thebottom of the converter. In addition, full extension carrier ram strokesto the end of each stage may be programmed to occur occasionally toprevent stagnant material from building up and agglomerating near theend of the stage. It will be apparent to the person skilled in the artthat other carrier ram sequences may be considered herein withoutdeparting from the general scope and nature of the present disclosure.

In order to optimize conversion efficiency, in accordance with oneembodiment of the present invention, the material is maintained at ashigh a temperature as possible, for as long as possible. Uppertemperature limits are set to avoid the material beginning to melt andagglomerate (e.g. form clinkers), which reduces the available surfacearea and hence the conversion efficiency, causes the airflow in the pileto divert around the chunks of agglomeration, aggravating thetemperature issues and accelerating the formation of agglomeration,interferes with the normal operation of the carrier rams, andpotentially causes a system shut down due to jamming of the residueremoval screw 2209. The temperature distribution through the pile mayalso be controlled to prevent a second kind of agglomeration fromforming; in this case, plastic melts and acts as a binder for the restof the material.

In one embodiment, temperature control within the pile is achieved bychanging the flow of process air into a given stage (ie. more or lesscombustion). For instance, the process air flow provided to each stagein the bottom chamber may be adjusted by the control system to stabilizetemperatures in each stage. Temperature control utilizing extra carrierram strokes may also be used to break up hot spots. In one embodiment,the air flow at each stage is pre-set to maintain substantially constanttemperatures and temperature ratios between stages. For example, about36% of the total air flow may be directed to stage 1, about 18% to Stage2, and about 6% to Stage 3, the remainder being directed to the GRS(e.g. 40% of total air flow). Alternatively, air input ratios may bevaried dynamically to adjust temperatures and processes occurring withineach stage of the gasifier 2200 and/or GRS 3200.

Plasma heat source power (e.g. plasma torch power) may also be adjustedto stabilize exit temperatures of the GRS 3200 (e.g. reformulatingchamber output) at the design set point of about 1000 degrees C. Thismay be used to ensure that the tars and soot formed in the gasificationchamber 2202 are fully decomposed. Addition of process air into thereformulating chamber 3202 may also bear a part of the heat load byreleasing heat energy with combustion of the syngas. Accordingly, thecontrol system may be configured to adjust the flow rate of process airto keep torch power in a good operating range.

Furthermore, converter pressure may be stabilized by adjusting thesyngas blower's 6250 speed, in the embodiment of FIG. 1, depictedproximal to the homogenization subsystem input. At speeds below theblower's minimum operating frequency, a secondary control may overrideand adjust a recirculation valve instead. Once the recirculation valvereturns to fully closed, the primary control re-engages. In general, apressure sensor 8110 is operatively coupled to the blower 6250 via thecontrol system, which is configured to monitor pressure within thesystem, for example at a frequency of about 20 Hz, and adjust the blowerspeed via an appropriate response element 8113 operatively coupledthereto to maintain the system pressure within a desired range ofvalues.

A residue melting operation is also performed in a continuous operationin a separate vessel (e.g. RCC 4220) which is directly connected to theoutlet of the converter 1200. The residue is removed from thegasification chamber 2202 by a toothed screw conveyor (residueextraction screw) or the like mounted at the end of the gasifier 2200and fed into the top of the RCS 4200 via a series of screw conveyors,for example. A small stream of particulate from the bag house 6230 mayalso join the main stream of residue via screw conveyors, for example,for further processing.

The RCS 4200 is a small, refractory-lined residue conditioning chamber(RCC) 4220 with a 300 kW plasma torch 4230 mounted into the top, aprocess gas outlet 4228 connecting a gas treatment skid, and a moltenslag outlet 4226. The gas exiting the gas treatment skid may be directedto join the main stream of syngas from the converter 1200 at the inletto the main baghouse 6230, or directed alternatively for furtherprocessing. In this example, the residue drops directly into the top ofthe RCC 4220 where it is melted by close contact with the plasma torchplume 4230. The molten slag is held-up, for example, by a vee-notch weir4224 inside the RCC 4220. As additional residue particles flow into theRCC 4220 and are melted, a corresponding amount of molten materialoverflows the weir 4224 and drops into a water-filled quench tank 4240integral with a screw conveyor where it solidifies, shatters into smallpieces of glass-like slag, and is conveyed to a storage container.

In controlling the residue processing, the power of the plasma torch4230 may be adjusted as needed to maintain temperatures adequate for themelting operation. The RCC 4220 temperature instrumentation (e.g.temperature sensing element 8106) may include, for example, two opticalthermometers (OT's) which measure the surface temperature of the surfaceupon which they are aimed, 3 vapour space thermocouples mounted inceramic thermo wells above the melt pool, and 5 external skin mountedthermocouples mounted on the outer metal shell. The RCC 4220 may alsoinclude a pressure transmitter for measuring process pressure (e.g.pressure sensing element 8112) inside the RCC 4220.

One melt temperature control strategy contemplated herein is to measurethe delta temperature being observed by the two optical thermometers.One OT is aimed at the melt pool below the torch 4230, the other at themelt pool near the weir 4224. If the temperature near the weir 4224 iscooling off compared to the temperature below the torch 4230, then moretorch power is applied. An alternative is to use the OT temperaturesdirectly. A set point in the range of 1400-1800° C., known to be abovethe melting temperature of most MSW components is entered into thecontroller. Torch power is then adjusted as required to meet this setpoint.

In general, the level is not measured directly, but is inferred by bothOT temperature and vapour space thermocouples. If the temperature fallsbelow the temperature set point, this is an indication of un-meltedmaterial and interlocks will be used to momentarily slow the feed rateof residue, or to shut down the RCS 4200 as a last resort. The rate ofmaterial flow may be controlled by adjusting the RCC feed screw conveyorspeed via drive motor variable frequency drives (VFD's), for example.The feed rate may be adjusted as required to ensure acceptabletemperature control, within capability of melting rate of plasma torches4230, and to prevent high levels in the RCC 4220 due to un-meltedmaterial. In general, there may be some hold-up capacity for residuebeyond Stage 3 in the gasification chamber 2202, but sustained operationwill depend on the RCC 4220 having adequate melting capacity matchingthe steady-state production of residue.

The pressure in the RCC 4220 may be monitored by a pressure transmittertapped into the vapour space of the vessel (e.g. element 8112). Ingeneral, the operating pressure of the RCC 4220 is somewhat matched tothat of the converter gasification chamber 2202 such that there isminimal driving force for flow of gas through the screw conveyors ineither direction (flow of solid residue particles only). A control valve8134 is provided in the gas outlet line which can restrict the flow ofgas that is being removed by the downstream vacuum producer (syngasblower). A DCS PID controller calculates the valve position needed toachieve the desired operating pressure.

Beyond the start-up phase, a back-to-front control, or demand-drivencontrol can be used where the gas engines 9260 at the back-end of thegasification system 120 drive the process. The gas engines 9260 consumea certain volume/hr of fuel depending on the energy content of the fuelgas (i.e. product gas) and the electrical power being generated.Therefore the high level goal of this control system is to ensure thatadequate MSW/plastics feed enters the gasification system 120 and isconverted to syngas of adequate energy content to run the generators atfull power at all times, while adequately matching syngas production tosyngas consumption such that flaring of syngas is reduced, or eveneliminated, and the electrical power produced per ton of MSW consumed isenhanced, and preferably optimized.

In general, the front-to-back control scheme described above comprises asub-set of the back-to-front control scheme. For instance, most if notall process control goals listed in the above scheme are substantiallymaintained, however the control system is further refined to reduceflaring of syngas while increasing the amount of electrical powerproduced per ton of MSW, or other such feedstock, consumed. In order toprovide enhanced control of the process and achieve increased processefficiency and utility for a downstream application, the flow of syngasbeing produced is substantially matched to the fuel being consumed bythe gas engines 9260; this thus reduces reduce flaring or otherwisedisposition of excess product gas from the gasification system 120, andreduces the likelihood of insufficient gas production to maintainoperation of the downstream application. Conceptually, the controlsystem therefore becomes a back-to-front control (or demand-drivencontrol) implemented such that the downstream application (e.g. gasengines/generators) drive the process.

In general, in order to stabilize syngas flow out of the converter 1200in the short term, the air additive input flow into the converter 1200may be adjusted, providing a rapid response to fluctuations in gas flow,which are generally attributed to variations in feedstock qualityvariations (e.g. variation in feedstock humidity and/or heating value).In general, effects induced by an adjustment of airflow will generallypropagate within the system at the speed of sound. Contrarily, thoughadjustment of the MSW and/or plastics feed rate may also significantlyaffect system output (e.g. syngas flow), the feedstock having arelatively long residence time within the converter 1200 (e.g. up to 45minutes or more for this particular example), system response timesassociated with such adjustment will generally range at about 10 to 15minutes, which on the short term, may not be sufficient to effect theproduct gas in a timely manner to avoid unwanted operating conditions(e.g. flared excess gas, insufficient gas supply for optimal operation,insufficient gas supply for continuous operation, etc.). While stillhaving a slower response than an increase in airflow, an increase in MSWfeed rate may result in a faster response than an increase in PLASTICSFEED because the moisture content of MSW may produce steam in about 2 to3 minutes.

Accordingly, adjusting total airflow generally provides the fastestpossible acting loop to control pressure and thereby satisfy input flowrequirements for the downstream application. In addition, due to thelarge inventory of material in the converter 1200, adding more air, orother such additive, to the bottom chamber does not necessarily dilutethe gas proportionately. The additional air penetrates further into thepile, and reacts with material higher up. Conversely, adding less airwill immediately enrich the gas, but eventually causes temperatures todrop and reaction rates/syngas flow to decrease.

Therefore, total airflow is generally ratioed to material feed rate(MSW+plastics) as presented in FIG. 45, whereby an increase in additiveinput will engender an increase in feedstock input rate. Accordingly,the control system is tuned such that the effect of increased air isseen immediately, whereas the effect of the additional feed iseventually observed to provide a longer term solution to stabilizingsyngas flow. Temporarily reducing generator power output may also beconsidered depending on system dynamics to bridge the dead time betweenincreasing the MSW/plastics feed rate and seeing increased syngas flow,however, this may not be necessary or expected unless faced with unusualfeedstock conditions. While adjustments to airflow (the fastest actingcontrol loop) and adjustments to the fuel to air ratio and the totalfuel rate (both longer term responses) are preferred in this example tomaintain suitable gas characteristics for the downstream application,the MSW to plastics feed ratio control is not necessary, but may act asan additional control used to help smooth out long term variability.

In this example, MSW moisture content generally varies between 0 and80%, and heating values vary between about 3000 and 33000 kJ/kg, and theHC has a 2 minute residency time and generally a pressure of about 210mbar. A variation of about +/−60 mbar is possible without exceeding theminimum supply pressure for the engine of about 150 mbar. Without thecontrol system, the pressure can vary by up to about 1000 mbar, hencethe long term flow fluctuations are actively reduced by the controlsystem by up to 4 times (or 75%) in order to run the gas engine 9260 atconstant load as desired. Furthermore, pressure fluctuations of theconverter gas can reach about 25 mbar/s without the control system,which is about 2.5 times the maximum of about 10 mbar/s for the engineof this example (or about 60%). Hence, the control system of the presentinvention may reduce short time process variability by at least 2.5times (60%) and long term process variability by about 4 times (75%).Use of the HC 7230 in this example can help reduce the short termvariations.

The disclosure of all patents, publications, including published patentapplications, and database entries referenced in this specification areexpressly incorporated by reference in their entirety to the same extentas if each such individual patent, publication, and database entry wereexpressly and individually indicated to be incorporated by reference.

Although the invention has been described with reference to certainspecific embodiments, various modifications thereof will be apparent tothose skilled in the art without departing from the spirit and scope ofthe invention. All such modifications as would be apparent to oneskilled in the art are intended to be included within the scope of thefollowing claims.

1. A low-temperature system for the conversion of carbonaceous feedstockinto syngas of a defined composition, said system comprising: ahorizontally oriented gasifier for conversion of carbonaceous feedstockinto off-gas and residue, said gasifier having a feedstock inlet, gasoutlet and a residue outlet, and comprising a stepped floor, whereineach step is provided with a lateral transfer unit for moving materialthrough said gasifier during processing; a gas reformulating subsystemfor the conversion of off-gas produced in said gasifier into syngascontaining CO and H₂, a residue conditioning subsystem for melting andhomogenizing said residue, and a control system to regulate theoperation of the system.
 2. The low-temperature system of claim 1further comprising a heat recycling subsystem for reclaiming heat fromsaid reformulated gas and recycling said heat to the gasifier.
 3. Thelow-temperature system of claim 1 or 2 further comprising a gasconditioning subsystem for removal of a majority of particulate matterand at least a portion of heavy metal contaminants from said syngas toprovide conditioned syngas.
 4. The low-temperature system of claim 3further comprising a gas homogenization system for receiving saidconditioned syngas and providing substantially homogeneous conditionedsyngas.
 5. The low-temperature system of claim 1, wherein the controlsystem is configured to sense a composition of the syngas, compare saidcomposition with said defined composition, and operate one or moreprocess devices of the system in a manner conducive to adjusting saidcomposition within a range of said defined composition.
 6. Thelow-temperature system of claim 5, said gasifier comprising one or moreinlets for the input of one or more process additives therein, whereinthe control system is configured to sense a composition of the syngas,compare said composition with said defined composition, and adjust saidinput of process additives to adjust said composition within a range ofsaid defined composition.
 7. The system of claim 1, wherein each saidlateral transfer unit comprises a carrier ram.
 8. A method for thelow-temperature conversion of carbonaceous feedstock into syngas, themethod comprising the steps of: providing a horizontally orientedgasifier comprising two or more laterally distributed processing zones;feeding the feedstock to a first zone of said gasifier; laterallytransferring said fed feedstock through each of said zones for enhancingconversion of the feedstock into off-gas; reformulating said off-gasinto syngas containing CO and H₂, conditioning a residue produced fromthe conversion process by melting and homogenizing said residue.
 9. Themethod of claim 7, wherein the laterally transferring step of feedstockis operated and controlled by a control system adapted to monitor atransfer of the feedstock and adjust a lateral transfer of saidfeedstock in response thereto.
 10. The method of claim 8, wherein saidcontrol system monitors said transfer via feedstock height sensorsdisposed within the gasifier.